What is the progression route in Terraria?

I'm kind of stuck in Terraria. I have full silver armor and 12 hearts (gold/silver gear).

I have just killed the Eye of Cthulhu.

I was thinking about gathering gold armor, but gold is damn scarce. I have tried searching for floating islands (at 406 altitude) but if I go to far I get attacked by Harpies, and I can't build a sky bridge and fight them at the same time.

My meteorite landed in corruption and it's impossible to collect it (I get swarmed by meteor heads with no way to run).

So what is the most natural progression? Should I try and find gold (where?), try to kill the Eater of Worlds, try to mine meteorite or try to fight off imps and collect some hellstone?

Here is what I ended up doing:

• Searched for Gold to create gold armor and weapons (doubtful you'll get full gold gear)
• Killed the Eye several times for Demonite Ore
• Destroyed two Shadow Orbs for their drops (the third spawns the boss Eater of Worlds)
• Dynamite the Meteorite and Magic Mirror out of there (after enough of it is mined out, the meteor heads will stop spawning) then use a gold Pickaxe or higher to mine the Meteorite.
• Floating Islands. Craft your skyways during the day, the spawn rates are higher at night for Harpys. Remember these skyways disrupt Meteors, making them very non-profitable.
• Explore under the surface! There are plenty of hearts and chests filled with great magic items! You don't need to go too deep either. Try natural caves.

Now is also an excellent time to farm hearts and stars, and participate in the Blood Moon event for cash. I think the game gets really fun once you get over this little hump in character progressions.

I tended to make little goals like:

1. I will mine this meteor.
2. Then I will look for hearts.
3. Then I will search for floating islands.
4. Then I will destroy another shadow orb.

You get the idea.

EDIT: Sorry I can't provide links, at my desk and unable to reach the wiki.

EDIT2: See this question/answer as well for a similar problem.

Robb's answer is very good, but I am going to offer up a more detailed, and alternate path.

The high level version is:

1. Beeline for shadow stuff, get into the dungeon, loot the skyworld.
2. Tunnel to the bottom of the world so we can mine Hellstone and kill the Wall of Flesh (And then farm him for fun things).
3. Hardmode!

The Early Game, or How I Farmed the Eater of Worlds for fun and profit

Our goal here is the famed Eater. He drops shadow ore and shadow scale, which we can use to make gear that will tide us over until we can farm Hellstone at the bottom of the world. Honestly, it's probably easier to get a full set of shadow armor than it is to get a full set of gold, depending on how lucky you are with ore field spawns in the natural caves. We want meteor ore, but it's a luxury, and we're not going to maximize meteor spawns (which would mean breaking one shadow orb a day only).

Starting out: Explore the natural caves that generate in the world, looking for chests, hearts, and ore (iron, silver, or gold only). Note there are a couple of things in particular we want from chests. Wood chests can contain iron bars and Gold chests can contain silver and gold bars. These are exceptional finds; a stack of 10 gold bars can take awhile to farm naturally. We also need bombs, not grenades. Dynamite is great but it's rarer; we need as many bombs and dynamite as we can get our hands on. Also, we need spiderwebs to make a bed (takes 50 webs; eventually we will want more than one bed, most likely). Collect gems too; we need at least 10 of one color.

For our home, it's best to set up shop near a swath corruption or the dungeon. Ideally, nearish to both.

A magic mirror is borderline critical. It will really help us in these next parts, but remember you can save and quit to simulate "town portal". Boots of speed and the Cloud Bottle are the only two accessories we really have a hearts set on. An enchanted boomerang is a minor luxury. Horde money, of course.

Crafting: Iron pickaxe first, then make armor from the best stuff we have. Make Iron broadsword and bow after this, if desired. Make 3 iron chains and save them for the grapple hook. Hope to farm the hook down in the stone layer (it makes a lot of things easier but is not strictly speaking necessary for the next part).

Savvy look ahead type stuff farm death weed, glowing mushrooms, cacti, daybloom, mushrooms. Have some extra iron ore lying around. These are ingredients to make some key potions.

The Corruption

Needs: 7-8 hearts, minimum (140-160 hp, but if you're very good you can get by with less), at least iron armor. Lots and lots of bombs/dynamite. A grappling hook or some other way to survive the falls (we'd prefer to speed this part up, but you could use a series of platforms/careful hugging of walls when they go concave/etc to get to the bottom). And a little bit of luck. Ideally, we could bring regular healing potions, thorns potions, iron skin potions, and regeneration potions.

Ordinary play would see us break one shadow orb a day, to maximize the chance for meteors to fall. Meteor ore has a few awesome and a few solid uses. But it's not critical to our strategy. With iron+ armor and an iron skin potion we're now quite resilient. A band of regeneration and a regen potion will probably see us not needing to heal too much. Our biggest problem is going to be hurting the Eater himself. A little luck will solve that problem shortly.

We want to break 2 orbs ASAP. Our hope? A Ball O' Hurt drops. The Ball of hurt, + the above setup, will make the Eater fight almost too easy, as the ball will frequently hit 3-8 sections at a time, doing multiple hits to each. Patience, and the occasional heal, and he's ours. And then we can easily kill him 3-5 times, and make a hole bunch of awesome things. What if we don't get the ball (20% drop chance from an orb)? Well, you have a few options. Note: you are more likely to segment the Eater a lot with the Ball. With Gold armor and those potions, I have not found this to be an issue. YMMV.

Ranged weapons bows are slower than we like, but with unholy arrows you get piercing (need worm teeth to make these). A musket is ok, better with meteor shot, though that requires meteor farming. A better option? Shurikens. Save all Shurikens while you are doing your initial exploring. Take a big ole stack into the fight. They pierce, which again means "worm splitting" but you should be well defended enough not to care. I finally tried this method and they worked wonderfully. It's much easier to have 200+ shurikens lying around than hope for a Ball O Hurt as well. IIRC, I used about 130 on my shuriken kill.

Vilethorn is excellent, but it requires a lot of mana to use. Note, even if you don't have the mana for more than a swing or two, keep it on switch (unless you have Hurt), and switch to it every time mana tops off.

Desperation: if you have to fight the goblin army, you will collect a lot of spiked balls. Line the bottom of your "arena" with them, and the Eater will take a bunch of damage over time coming and going.

Also, you can always crack a third orb and just let the eater kill you. There's more than enough orbs on a medium sized world to farm him many times over. A Ball O' Hurt is really our heart's desire.

The actual fight isn't too hard- make an arena with wooden planks on several levels in one of the more open areas in the huge horizontal layer in this section of the corruption. Wall off most of the top and part of the sides, to minimize unwanted guests getting in. Once you open the third orb, head straight to it.

What to craft: Shadow pickaxe first. Then shadow armor (will need scales here). Then a melee weapon and maybe a bow, depending on your needs. If you've managed a phase blade, don't worry about making a melee weapon.

Meteor ore: we want this eventually, but our only needs here are really meteor shot and enough bars to make a phase blade perhaps (20 meteor bars, 10 gems of a single color). Using dynamite to mine it is a huge time saver and also a frustration saver. We don't care about the armor. A hamaxe is a luxury. The Space gun - made from meteor among other things - is nice but also mana intensive (less so than Vilethorn). Note, large weapons with good attack speeds can be very effective against the Eater.

Welcome to the Jungle

You don't need to go to the jungle at this point (or before now, by the by that's an option but this path is probably easier for neophytes), but you can. The Jungle has one thing we covet above all others: the ability to make the Ivy Whip, which is a huge upgrade to the grapple hook. That said, the Grass Sword and the Grass Chakram can be very useful, so if you want to farm them, do so. But you will want an Ivy Whip eventually.

The Dungeon: A Golden Ticket to Golden Keys

Once you have a grapple hook (or the whip), shadow gear, a decent ranged option, and a stack of potions, it's time to kill skeletor. Once again you want to make an arena outside the dungeon. A musket is great for this fight, don't necessarily waste meteor ammo (we have something else we want to use that for). But the Ball or some other melee weapon can be used. So can a Grass Chakram. Wait until night, summon Skeletron forth, and then killing.

Needs: there are a lot of nice items in the dungeons, but we have only 4 needs really.

Free the NPC that will spawn inside: make sure you have an empty room to hold them.

Find a shadow key in a chest: just because.

Find a cobalt shield in a chest: we'll want it later.

Farm golden keys: Ww need them to open the vast majority of chests in the dungeon. But we also need them to loot the sky islands, if we want to go that route (I recommend it).

There are other nice items, don't get me wrong. Muramasa, some nice magic options. An upgrade to the Ball O' Hurt. And you will make a lot of money. Also, if you aren't topped off in heart containers you will be after a couple of dungeon runs. Also, the handgun has crafting potential.

Sky Islands in The Jetstream

Again, not necessary, but the path to real ultimate power is eased with a few toys found therein: The Golden Horsehoe (no more damage from falling!) and red balloon (jump higher). It does take some effort to get up to them (and to find them, in fact, unless you use a mapping program for that).

The House At The Bottom of The World

And now, we're ready. We have a shadow pickaxe. We have shadow armor. We have many wonderful toys. It's time to dig the so called "hellevator", straight down to the bottom. This will take awhile, but it can be an oddly meditative experience I've found. Put on your favorite music (I used to use Big Dipper's Anthology), kick back and relax as you shape the world into something of your own making.

First order order of business? Farm Hellstone. It's time consuming, but we want a full set of Hellstone gear and a Hellstone pickaxe. All else is optional. If you can find a shadow chest, loot it. There's good stuff in those.

What next? At this point you really need to hit the jungle if you haven't. Now is also a good time to hit the sky islands, because we're about to move this game into some Nth Gear that is both exciting and difficult to handle at the same time.

Lastly, by this point you should have freed several NPCs, including the Goblin Tinker. Now is a good time to avail yourself of his excellent services. You can make several "super accessories" and should so so. Once you are very wealthy, you can reforge items to get better bonuses on them (very expensive, though). He does sell rocket boots. Trust me, you want the rocket boots.

The easiest way to kill the Wall of Flesh is build a hugely long horizontal platform (yes, this will take awhile). At the far end, you summon him and then be about your business. The easiest way to kill him is ranged weapons by far. Meteor shot is invaluable because it will pierce, and you can hit multiple things. I recommend using the Minishark (purchased from the arms dealer). It has low base damage, but it shoots so fast and will conserve quite a bit of ammo. Killing the Wall of Flesh will activate Hard Mode. You can farm him over and over, getting some rather choice drops and making quite a bit of money. Advanced players would use a combination of feather fall, speed, and gravitation or maybe water walking, obsidian skin, and speed to avoid needing to make the bridge. But I like making the bridge. It's my time to reflect on all the fun that came before, and all the new friends I get to make after killing the Wall.

And Hardmode is now open and waiting for you to explore it. It's much more difficult once you're in the new content (as it were, and no it's not everywhere at once). However, it's incredibly rewarding. 3 New bosses, a bunch of new enemies, and a boatload of new items all waiting for you to play with. You will be feeling invincible once you're ready to face the Wall of Flesh and Hardmode will disabuse you of that notion. But you'll claw your way back to invincibility and then beyond, to double plus invincibility with a helping of Power Puff Girls for good measure.

The answers on this question are a bit outdated, so I'll try to give a more general overview of the game's overall progression.

Most people use their current level of armor/weapons as a general benchmark of how far along in the game they are. After all, the stronger the equipment, the stronger the enemies they can face. This is why I use equipment tiers as a guide for progression.

I'm only going to explain bosses, biomes, and equipment tiers in this answer - otherwise this answer would get much too long.

Early Game Setup (Basic Ores + Wood)

When you first start the game, the only tools you have available are a Copper Shortsword, Copper Pickaxe, and Copper Axe. You've got no armor, no (good) weapons, and no accessories. The strongest ore you can mine at this point is gold/platinum, so all equipment using those ores fall into what I would consider the early game. This is usually the time when you're collecting basic resources - not just ores (copper/tin, iron/lead, silver/tungsten, and gold/platinum), but also wood, stone, potion ingredients, ammo, money, etc. You'll typically build a few houses for NPCs in preparation for upcoming events.

Early Pre-Hardmode (Shadow and Meteor)

After getting some decent weapons/armor and upgrading your health, you'll typically start killing two of the stronger early game bosses: Eye of Cthulhu and Eater of Worlds/Brain of Cthulhu (for Corruption and Crimson worlds respectively). Both bosses drop demonite ore, which is required to make some of the mid-tier prehardmode tools. Eater of Worlds/Brain of Cthulhu also drops Shadow Scales/Tissue Sample, which is needed for the actual Shadow armor.

Once you destroy a Shadow Orb or Crimson Heart, meteors will also start to spawn (50% at midnight for each orb/heart you destroy). Standing close to meteor biomes will cause Meteor Heads to spawn en masse, though they are luckily easy to kill. You can craft Meteor armor using the ore you mine, as well as some cool weapons.

Shadow armor is the melee armor at this level, and Meteor armor is for mage characters. At this point there is no specialized ranged armor.

Mid Prehardmode (Jungle and Dungeon)

Now that you've got some decent protection, you can face the dangers of the jungle and the dungeon. Personally, I usually go to the dungeon first so I have stronger weapons to use in the jungle, but it's quite viable to go to the jungle first.

To get in the dungeon, you first need to beat Skeletron by talking to the man outside at night. If you don't beat Skeletron first, you'll summon a Dungeon Guardian as soon as you move too far down - this monster is very fast and will instantly kill you when you touch it (this is even true if you had the best armor in the game). Rewards from the dungeon include the Muramasa, Cobalt Shield, Handgun, and other goodies. You'll also find plenty of bones from the skeletons you beat, which can be used to craft Necro armor. This is the first armor that is geared toward a ranged character.

In the jungle, you'll be facing a bunch of mobs that do a lot of damage, so be on your guard. Your primary purpose in coming to the jungle is to collect jungle spores, stingers (from hornets), and vines (from man-eaters). These items are used to craft jungle weapons and the jungle armor. The armor is geared toward mage characters (specifically for mana usage, IIRC).

The jungle is also home to the Queen Bee, a semi-difficult boss (at this level anyway) that drops Bee Wax. Bee Wax is used in crafting Bee Armor, the only armor set prehardmode that is meant for summoner characters. It increases the total number of minions you can have out to 3 total, and also increases minion damage.

Late Prehardmode (Molten Armor)

Once you've got stronger gear, you're ready to go to hell. The underworld is an area filled with lava and powerful enemies. Your goal in this biome is twofold:

1. Get enough hellstone to be able to craft molten armor, the most powerful melee-focused armor in prehardmode
2. Find a Guide Voodoo Doll to summon the Wall of Flesh.

If you've got strong enough equipment, drop a guide voodoo doll into the lava and fight the Wall of Flesh. Beating this boss will commence hardmode - enemies are tougher, new biomes are available, and the Corruption/Crimson will spread much faster.

Early Hardmode (Hardmode Ores + spiders)

Once hardmode starts, the first thing you'll want to do is smash as many demon altars you can using the Pwnhammer (which should have dropped from Wall of Flesh). Each time you do, more hardmode ores (cobalt/palladium, mythril/orihalcum, adamantite/titanium) are added to the world. You'll need to mine these ores to upgrade your gear, otherwise the upcoming bosses are going to kick your butt! You'll also be upgrading your crafting stations at this point - specifically, you'll upgrade your anvil to a mythril/orihalcum anvil and your furnace to an adamantite/titanium furnace.

Note that each tier of ore comes with three different helmets you can craft. Each helmet changes the focus of the armor to be either melee, ranged, or magic oriented.

One other armor that is available now is the Spider armor, which you can craft using the spider fangs from Black Recluse in spider lairs. Spider armor is the strongest summoner armor you can get at this point. Be very careful though - Black Recluses do a lot of damage, and they also inflict the Venom debuff, which is a much stronger version of poison. Without upgraded gear, it's very possible for them to 2-3 shot you.

Early Hardmode Bosses (Hallowed armor)

In prehardmode, you could fight any bosses in any order and still progress through the game. Sure, it might be harder to fight Skeletron before Eye of Cthulhu, but you could still do it if you wanted. That is not the case in hardmode anymore - stronger bosses are now only available once you've beaten the lesser bosses. In this case, your progress is gated by the mechanical bosses.

The mechanical bosses (The Twins, Destroyer, and Skeletron Prime) can be beaten in any order, but you have to beat all three. Each of them will drop a special soul type, as well as a bunch of Hallowed bars. Hallowed bars can be used to make Hallowed armor and weapons, all of which are quite good at this level. Once you beat all three mechanical bosses, you'll get a message ("the jungle grows restless") and Plantera bulbs will begin to spawn.

Mid Hardmode (Chlorophyte, Tiki, and Turtle armors)

Now that the mechanical bosses are defeated, you should have enough Hallowed bars to make a Pickaxe Axe or the Drax. Both of these items are able to mine Chlorophyte, a plant-based ore that is used to craft chlorophyte armor. Additionally, you will begin to find Plantera bulbs spread out within the jungle. Breaking one will summon Plantera, a powerful boss that guards the jungle. Beating Plantera will reward you with a Temple Key and a random piece of equipment. If you get a Pygmy staff, you are able to buy Tiki armor from the witch doctor if 1) he lives in the jungle biome, and 2) you have the Pygmy staff in your inventory when you talk to him. Tiki armor is an upgraded version of the Spider armor and grants additional summoner bonuses.

If you're planning on going melee, you might want to consider using your chlorophyte to craft turtle armor instead of regular chlorophyte armor. Turtle armor is a defensive armor which is not focused on any specific discipline of playstyle (melee, ranged, or magic) - however, it can later be upgraded to a stronger melee-based armor.

Prepping for End Game (Beetle, Shroomite, Spectre, and Spooky Wood armors)

Once Plantera is beaten, the Truffle NPC will sell the Autohammer, a crafting station that will let you craft Shroomite armor. Shroomite armor is the current strongest ranged-focused armor you can get. There are three varieties of Shroomite helmet, which will grant bonuses to arrow-, bullet-, or rocket-based ranged attacks depending on which one you're wearing.

Once you've obtained the Temple Key from Plantera, you can now access the jungle temple. Unlock the door and head to the bottom, where the Golem awaits. Beating the Golem will reward you with beetle shells, which can be used to upgrade your turtle armor into either an offensive or defensive melee-focused armor.

Beating Plantera also causes new enemies to spawn in the dungeon - and it also allows you to open any of the special biome chests. If you head over to the dungeon, you'll notice some creepy cultist people worshiping a floating symbol. Leave them alone for now, unless you're prepared for the end game/don't need anything from the dungeon. Enter the dungeon and start fighting the new monsters. Any monster with over 100 HP has a chance of spawning a Dungeon Spirit after death. Dungeon Spirits drop Ectoplasm, which is used to craft Spectre armor, a mage-focused set that can be either offensive or defensive depending on the helmet type you wear.

Once you have access to Ectoplasm, you can also craft a Pumpkin Moon Medallion which will start the Pumpkin moon event when used. Among other things, you can find Spooky Wood during this event, which can be used to craft the Spooky armor for summoners. Spooky armor has less defense than Tiki armor, but it allows you to summon one extra minion, so it's a bit of a tradeoff.

End Game (Celestial armors)

Once you're ready for end game, you can summon the Lunatic Cultist by killing the weaker cultist at the dungeon's entrance. Beating the Lunatic Cultist will make 4 pillars spawn on your world. These pillars aren't a boss fight per se, but they are definitely more drawn out battles than usual. Each pillar, once destroyed, will drop fragments that can be used to craft powerful endgame weapons.

Once all four pillars are destroyed, you have about 30 seconds to a minute before the "final" boss of the game, Moon Lord, spawns on top of you. This is definitely the toughest fight in the game, but beating him will reward you with Luminite ore, which is used in combination with the fragments from the pillars to craft the Celestial armors. Each armor is focused on a different discipline: Solar armor is for melee, Vortex is ranged, Nebula is magic, and Stardust is summoner. These are the strongest armors available in the game for each class.

Disclaimer

This answer is merely a guide to the most basic progression path in Terraria. Despite the length of this post, I left out a lot of detail and optional equipment because otherwise this post would be too long.

If you'd like to see the progression of every boss and/or invasion available in game, please see my answer to this question for more details.