IMHO, the best early game strategy is as follows:

1. Unload all pop from first colo ship onto earth and take only 0,5. Use this colo ship to colonize a planet FAR away
2. Set earth 100% science, rush buy 2 Labs on earth (on turn 1 and 2), reasearch Int. Travel, Specialization (+1 moves) and ion drives as the first 3 techs. Should be done on turn 12~
3. Rush buy the cheapest colo ship (should be 690 credits) and colonise Mars (ALL colo ship leaving earth will take ONLY 0,5 pop each)
4. Fill mars with only factories (set 100% manu untill done). When all fac are done, set 100% military
5. Buy 1-2 factories on earth, reduce science (around turn 8-10, but leave still enough research so u complete ION Drives around turn 12-14)
6. When ion drives is done, reduce science on earth to a minimum, set 90% Military rest manu for completing more factories
7. When you colonise the second planet (in addition to mars), either with the coloship u started with (only if u find a very good planet far away from Earth) or with another cheap colo ship to a nearby one, build 1 fac there, then science building and use this to support science for the early game (while Earth and Mars are set to 100% Military to sapm coloships)
8. As first Ideology take Pragmatic (3 free ships). Upgrade them to colo and use them(always 0,5 pop)
9. Tech order: Int trave --> Specification (+1 moves) --> ion drives. After this I usually go for the one that gives hospitals then xeno commerce and the approval specialisation

On turn 4-6, as soon as int travel is done, u should rush buy a maxed out sensor ship.

By turn 14 you should be able to produce 1 Coloship (with IOn Drives, 11 moves and 25-40 range) in 2 turns.

A cargo hull ship, that holds as many sensors as it can carry and nothing else.

I am no expert on GC3 (yet) but after playing 100+ hours, there's a few things I have figured out for myself.

1) Get that research tree up and going FIRST.  Since ALL future research depends on your research capability, I go for that tree first in all 3 ages.
2) Next up (for me) is production.  Going for universal translator and starting to work up the government tree will eventually give good production bonuses, that's important to me. (industrial specialization doesn't hurt, but you want the production bonuses as soon as you can get them.)
3) Throw some points into the interstellar research tree.  That gets your ships moving faster and farther early on which will save you HUNDREDS of moves later in the game.

Once I have those 3 built up to at least the end of the first age, then it's time to decide what greater strategy I'm going after.  For me that's usually dumping a lot of points into the military tree, while slowly adding points to some of the others.  I start alternating between military and other tech trees.  So for every one thing I research in military, I pick one other tree to dump a point into, while paying attention to make sure my research and production tress stay ahead of the game.

But of course this all depends on what race you are playing and what type of win you are going for!

I'm sure it's like Diablo where there really are millions of possible combinations and strategies for getting there.

My build strategy is for a military based civilization, but I think at least the research portion of the build is a winner for any type of strategy.  Everyone has to research, and the faster you can do it the more options you have available to you.  I SPAM research buildings on any planet I can fit them and pay attention to those adjacency bonuses on planets!  Antimatter reactors and advanced research buildings are your best friend.

One thing I should add to this is that even though I go for research first in the tech tree, I actually start industry on my home world before the research centers.  It's kind of a catch 22, but the way I see it is that I can't build research facilities fast enough if there are no factories to speed up building them up.  Right? 

So far this has all worked, but I should add that I play on insane maps at normal or slow game speed. 

Hope this helps and have fun!

100 hours in the first step in a 1000 mile journey.