How to level up past level 25?

With the release of The Taken King, light level and character level have been separated and the progression system has been redesigned.

Character level now progresses all the way to 40, rather than stopping at 20. Continuing to level beyond 20 is simple - you gain experience points as normal. The main point of character level is to enable you to equip more powerful gear, which directly influences your light level.

Light is now the average of all your attack/defense values (in the 2.0 update, Attack and Defense values were rebalanced to reflect this). Your light level progresses as you acquire better gear, and is now affected by your weapons as well.

So, how do you obtain stronger gear in The Taken King? There are a few ways:

• Legendary Marks: these are the most obvious. Legendary Marks replace Crucible and Vanguard marks as the new currency du jour. Many quests reward Vanguard marks, but the primary way to obtain them is the Vanguard Heroic Strike playlist. Your first three strikes on this playlist per week per account award you an additional 10 Legendary Marks. These marks can be used to purchase Vanguard or Crucible gear (which still require reputation, but reputation is easier to acquire in The Taken King) or craft Year 2 Exotics.
• Strikes: While you're gathering your Legendary Marks in strikes, you have chances to obtain Vanguard gear as normal drops. A new mechanic added in The Taken King is chaining strikes: the longer you stay in a playlist without returning to orbit the better your rewards will be. Presumably this applies to Legendary Marks from the Heroic playlist, but I haven't been able to test that yet.
• Crucible: The Crucible rewards gear and Legendary Marks as well. Playing each week's featured playlist will earn you Legendary Marks, reputation, and a chance at Crucible gear. Lord Shaxx now offers quests and special bounties as well - completing all of these in a week will reward "nightfall-like rewards".
• Nightfall and Raiding: These require a pretty good light level already, but have very attractive rewards. Note that neither of these are matchmade: If you don't have friends who are willing to do this, I recommend using a service like destinylfg.com

Most gear, even when maxed out will not be able to get you to max level of 32. The only gear that will get you to level 32 is the gear you get from do the Crota Raid. Then if you max level them all and have 1 fully leveled exotic piece of gear you will hit level 32. It's much easier to get to level 31 though.

To get to 31 you only need 1 fully leveled exotic and the rest of your gear can be bought from the Vanguard or Crucible quartermaster. I recommend using an exotic Helm for your warlock because helms are more expensive to buy from the quartermaster than the other 3 pieces of gear.

The way I leveled my Warlock: Got an exotic helm and leveled it up. Bought Gauntlets, Boots, and Chest from Vanguard Quartermaster in the tower. Leveled those up. Now I am level 31.

A good way to get vanguard marks every day is to find Daily Public Events. You will get 4 marks every time you complete one and you can find them by using the website: DestinyPublicEvents.com. You can do them more than once per day. I know you can do it at least 3 times a day to get vanguard marks but you may be able to do them more than that. I can't remember if they stop after 3 times.

To get to Level 32: Play Crota raid as much as you can to get the raid gear now that you are level 31.

One last thing: The level cap will be raised from 32 to 34 with all new gear coming out in the newest expansion. The release date for the House of Wolves expansion is May 19th. The good news is that they will have a way to upgrade ANY legendary or exotic gear to be able to get you to level 34 when maxed out. So rest assured that the gear you are working towards now to get to level 31 or 32 will still be useful with the next expansion. Unlike how the last expansion made all our old gear practically worthless!

You might have all the legendary armor with 33 light, which would make you a lvl 31. The problem I see here is that you aren't upgrading them. They get more light as you upgrade them. Of you fully upgrade (incl. upgrade defense). And vanguard ranks are fast with bounties and patrol. Considering you do 5 bounties, it gives you ~350 reputation. The. it takes only 10 patrols to get 100 reputation (Note that Assasination patrols give you 25). If you have completed the Weekly nightfall strike, reputation gains are faster. You get about a quarter more rep. You get 31 instead of 25, 12 instead of 10, 125 instead of 100...

List of armor light (all fully leveled)

Crota's end gear and exotic armor = 36 light (full set level 32)

Vanguard, crucible and other common legendary armor = 33 light (Full set = level 31)

Vault of glass gear = 30 light (Full set = Level 30)

here is a list of light levels and the wiki page of light.