I consider star bases to mostly serve as intimidation factor. Since the only intimidation factor the AI looks at is the number on FP, I always go hangars. To answer the one and done or replenishment question, honestly no idea. The star base keeps enemies early/mid game from going places, but late game it makes sure they have to put a reasonable effort into coming in, which helps concentrate losses or give me time to respond, but they are really not much more than a speed bump.
How I build my fleets seems like such a vague question. Depends really. I break my fleets down into two groups as it gets late game. Fast groups that are responding to nonsense that are usually 1 titan+corvettes. I usually roll a titan + bazillion battleship fleets that serves as my door knocking fleets where speed isn't important, but rather holding a presence. I'd say that's a general idea, but there's more to it than that.
My favorite standard admiral trait is trickster by far, but there's reasons to have other picks. If your ships are surviving fights more often the enemies, especially if its a lot more often, it's easier to punch above your level in my opinion. Other than that, I'd say gale speed has a lot of merit in some fleets, especially if you can get him one of the levi speed boosts to stack with it.