Ok - so...
influence ones should be built in spaces where you want to influence other planets, or gain influence in "empty" or "unclaimed" space...
military should be built perhaps around your planets so you can defend better on attacks? or maybe even built near an enemy location that you plan on attacking...
economic should be built in the area of a planet that perhaps has a high economic gain to further improve it... or built near trade routes?
and mining bases effect your whole civilization? so if I find one that improves research, it doesn't need to be in the area of my planet?
I'm pretty new at the game - and I just recently started using starbases - as before it seemed like a waste of time.