I apologize to Richert, for not answering his questions fully, as I am also fairly new, jumping onto my metaverse game indiscriminately (here and there, in other words).
but, I do kinda have a piece of starbase advice for a newbie

...
Mumblefratz and (for lack of a better translation) "novacaine" have both the right idea: wait until you have your own style of playing before you start fretting about starbase deployment.
I've personally found starbases' Extremely helpful fully developed (economic ones, of course

), in the early - mid game when pirates "rule" the skies.
I find that when I only have up to defender researched, my Starbase's are lightyears ahead of that, for w/e (whatever) reason

.
So, when a lonely fleet of pirates happen upon one of my planets, apparently, instead of going for the *ahem* usually Un-defended planet (I know - I still stink at that; working on beginning game economy right now, really

), they go for the very much "BEEF-CAKE"'ed economy starbase which, to my eyes, seems to take them out in one shot (yes - the entire 4 ship fleet

), with only two hitpoints out of 48 (math time: 46/48) gone.
So, although this comment may say I'm "chaotic evil", I'm really, according to my present game "Saintly good" and I usually lean that way, so I get the best defense techs................or something

.
but my ethical alignment usu *we apologize. those responsible for this tangent have been sacked*.
What I'm trying to say is that starbases are anyone's guess, but I agree that for actually defending planets, I would choose a good kick-butt fleet over a military starbase any day

.
so far, in my ever-changing huge metaverse game I'm playing, I'm ready to attack the altarians and so am putting a combo of both influence and military SB's (starbases) on their borders.
I apologize for the length of this comment, and the inability to answer your actual questions, but just remember, just 'cause you have no bonus production from a 4-billion planet, does not mean it can't make exponential economic growth by placing a few (I usually do five on a ten

Planet quality planet) [ stock ]markets and thus, you will usually have good money for making all those expensive (around 1,111 bc) starbases away from your *chuckles* center of galactic gravity

.
-Joren out (for now

)