Command & Conquer 3: Tiberium Wars/Economy

Early in the game, and quite possibly later on, you are better off building two Tiberium Refineries and selling one, hence getting two Harvesters per Refinery. In addition you will need to periodically build Tiberium Silos in order to expand your cache size or your economy will be capped at a certain amount. (If you are playing as Scrin, you don't need to worry about that.)

Plus when playing as GDI it is advisable to begin at a relatively large tiberium field for GDI harvesters tent to gather tiberium much quicker. It is also noted that the scrin players should always create a growth accelerator at their tiberium field once they construct an extractor as this will increase tiberium growth quite a bit.