The Crypt is used to train troops. The higher the level of the Crypt, the more types of troops you have available and the more of them you can train. The Obelisk is where your troops are stored. The higher its level, the more total troops you can have. The best early troop combination to use is the Burglar and the Soldier. Send in a few Soldiers to draw fire from your opponent, then send in a set of Burglars to get as many resources as possible before the battle ends. After unlocking the Fatso, partner them with the Burglars instead of the Soliders. When going for more starts, use Fatso and Throwers along with some Bombers to go through the walls easily. If possible, add a few Bombardiers and Fire Starters. However, training the cheapest troops to win at the lowest cost is the best way to maximize your profits.