Thanks for the many replies. There are other building strat threads around, and I've tried to glean what I could from them. Sometimes it still helps to crystllize your thoughts in a new thread.
I usually set up a handful of ship builders with mostly factories right away. When I come accross reasearch bonus tiles, I put labs on them as soon as I can. Eventually, all the tiles get filled, but only at the pace which my economy can support.
This makes sense - the number of factories you build will depend on your money situation and immediate goals, leaving some space open for later. How many? Hmm. Back to the sandbox.
I always start building markets early on.
Can you build markets too early? When your population is low, they don't add much money. I will have to investigate the break-even point on those. Then again, it's easier to build now than go through all of your planets later...
As far as what to build, that depends on strategy. There are several including all research, all production, and all economy. I tend to use a hybrid production and economy approach.
Don't know if I could do without any of those - I think I need to get a better handle on how to use them all first. All econ buildings? Wow. I'm still working on the n00b strategy for now.