Set up a queue when you colonize a new planet, I often use something like:
fact, fact, fact, money, fun, think, farm, friend, think, money, think, think, money, think, think
fact = factory type improvements
money = improvements that increase your cash
fun = entertainment/moreale
think = research
farm (come on, you don't need this explained do you?)
friend = influence generating structures
I rarely stick to the plan, but it's a good way to start. If you find the little micromanagement this game has tedious, though, the turn-based empire-building genre might not be your style. I generally have 3-5 constructors popping every turn, and an influence starbase in every second sector like a chackerboard, if not more.