ORIGINAL: Shark7
ORIGINAL: MoloMowChow
You mentioned adding recreational and medical centers to the star bases, but what about the commerce center?
Commerce center is not necessary on the star base. Civilian freighters will simply dock with the planet in this case. As a player you will not notice any difference in gameplay.
Actually, I think Commerce Centers are a requirement on Starports.
Okay, there are still questions bouncing around so I'll throw a few of my strategy tips - they're not necessarily better or worse than what Shark7 uses, they're just an alternative.
Early game, I build one Small Spaceport per System, usually on the first colony to reach about 500M Population.
When things progress a bit I'll upgrade the most valuable colony in the system to a Medium or Large Spaceport.
Around early-mid game, once I've got one Spaceport per system, I'll cycle back and start building a Small Spaceport on the remaining planets as this will give them the Recreation and Medical benefits boost which will allow you to Tax them higher without a non-compliance.
Additionally, this will give you at least some defensive capabilities to your planets, additional Research capacity, and more Ship Construction yards.
Some will not see this, but I tend to play really long games (~100 years or more), so late game I can start redesigning/retrofitting Spaceports without Research Labs to save some maintenance costs.
I don't really do this for monetary reasons as my Economy is usually humming along, but at this point in the game I've researched everything so I don't need the Labs and I'll use the extra cash to give my Military an extra kick.