Early in the game, only two basic resources need to be managed. Fuel is obtained from the Oil Derrick and is stored in the Fuel Stockpile. Supplies are obtained at the Supply Drop and stored in the Supply Stockpile. Although both are important, Supplies a bit more important, because they are used to build and upgrade structures and defenses. Focus on storage over production. When doing single-player attacks to get more Fuel and Supplies, if your storage is at capacity they will be wasted.