I get you friend, I struggled there as well.
Shields, gunships, and hover are, what I would call, a "macro" factory. In the early game, it is good to have a "micro" factory to pressure the opponent, and it's more fun.
The point of a micro factory is less so to take out the opponent, and more so to force the enemy into making too many defenses. Raiders, assault units, nukes, air units, they are a good start.
Then, once the micro factory has forced too many defenses out of the opponent, the important decision is to switch to a more macro-oriented factory. The point of a macro factory is that it scales way better in numbers, unlike, say, rovers, or cloakbots. Tanks, shieldbots, gunships, hovercraft, those are good choices for a macro factory, as you have noticed already.
This is how to play the game the fun way. It might not be the most efficient, but this strat is mine. Let me know what you think, Zsword!