It is definitely not recommended to build everything available on every planet! Your economy would go down the toilet, no matter how good you are at counting beans.
Some guidelines:
~ On your very best PQ planet, build all manufacturing projects. Manufacturing Center, Manufacturing Capital, etc. This is because your output will be highest due to the high population they can handle.
~ It is my belief that you never need to build Planetary Defenses. The money wasters can still be defeated (hey, the AI's usually build 'em and I don't have too much of a problem taking their planets!)
~ Build Info Nets and Neural Nets only if you are very sure your economy can handle them. They are fairly large money drains and don't give much in return.
~ Build Entertainment Networks on all planets! Some may disagree with this, but try to maintain 100% morale without 'em (at least in the early game)!
The best policy is to pick and choose where you want to locate some social projects. It goes without saying that you should build Soil Enhancement and Habitat Improvement on every planet, since they cost nothing and give you huge benefits! Weigh the benefits of every option before deciding to build something. Remember that everything that has a +Economy is not always a bargain, as an item that gives a +5% Economy but costs 5 maint. is usually not a good deal.
This is just my opinion, and I'm sure there are many out there who will disagree with at least some of my ideas. Hope it helps!