What is the most effective raiding strategy/loadout to earn resources?

I've been playing the game a while, and as you get to higher levels there is a significant need to stockpile large quantities of resources before you can start the higher level upgrades (Town Hall level 9, Clan Castle Level 4, Barracks Dragons upgrade, etc). In order to accomplish this without racking up a huge credit card bill, it seems that you have to raid frequently and win big jackpots each time you do so. I have found this to be very challenging because:

• I can usually only string together 2-3 attacks feasibly, due to the time it takes to train units.
• Related to the previous point, I often spend almost my entire stock of units during a raid, in order to win.
• Also related, I have the tough choice of training strong units which take forever to train and are very expensive, or weak ones which train quick and cheap but get wiped out rapidly.
• I often find it hard to even find opponents with big stockpiles, and when I do I often can't beat them.

I see other folks climbing the ranks and getting the big upgrades, so I know there must be a better way. So what's the most effective unit loadout and/or strategy to get big resource payouts (sufficient to get the high level upgrades)?

A strategy that works for me is the standard giant-healer attack. Find and take out the air defense close to you by distracting the defenses with a couple troops, use a few wall-breakers to break the wall. Then send as many giants as needed to take out the air defense. Then you can deploy the healer and the giants will destroy most of the defenses with nearly no trouble, provided no air defenses. However, problems can often arise with this strategy. The wall breakers could die, the giants could switch to a different target. In the event of this, I find a healing spell as a good way to keep the giants alive until it is safe to deploy the healer. Place it in the spot the giants will go, or in the center of them if there attacking. For clan castle troops, a few troops will do the job. Usually a lightning spell can quickly kill a mob of archers/barbarians. Even if the air defense is still there, deploy the healer as far from it as possible. YOU NEED THOSE GIANTS! Anyway, once the defenses somewhere are taken out, deploy archers or barbs to take out some stuff. If something is out of range of a defense, shoot it down. I have used this strategy for a month, and it is very effective. I have not lost one battle since I started doing this. Understand this works differently for everyone. Hope this helps.

Two words: Collector. Raiding.

Raiding storages deep inside a base is costly, time consuming, and error prone.

What you want to find is a base that is idle, where the collectors have filled up and are near/outside the outer walls. With practice you'll see the signs - no league shield, gold bins full, etc. Finding one can take a while, so have enough gold on hand to skip 50-100 bases to find one.

Drop troops around the outside and destroy the collectors, then end the battle or fight on to 50% to conserve trophies.

Collector raiding can be done with a wide variety of troop loadouts, but one of the easiest and most popular is BARCH (Barbs & Archers) or a variant like BAM (BARCH+Minions).

At TH7 and TH8, I can typically find bases with 150k to 300k resources within 50-100 skips. The troop training cost is usually around 15-20k for this, depending on your troop ratios and troop levels. The skip cost for 50 skips is 29k at TH8.

That yields a profit of somewhere between 100k and 250k of both gold and elixir per raid. Couple that with the fast training time of the required troops, maybe throw in some boosted barracks, and you'll be maxing out your storages in no time flat.

With the addition of level 12 collectors, the profit margin has a chance to be even higher still.