hi XaviorFist,
A few things to start well:
All of this is happening at the same time, basically as soon as the game loads...
I like to build my capital ship factory first thing, as you get a free capital ship. I usually go for the colonizing cap, which is really helpful at getting planets quickly. Make sure you kill any siege ships before you colonize, but you can finish off the rest of the militia after you colonize, since they will focus on your cap and can't hurt the planet. You don't really need many other ships in the first 5 minutes of play, as your cap can kill neutral ships and colonize their planets just fine...Order of priority in colonization is something like closest 1. Asteroids 2. Deserts 3. Terrans 4. Ice 5. Volcanic 6. Dead asteroids. The last two will never give you positive income to speak of...
Build crystal extractors first, then metal. Crystal will usually be more scarce than metal throughout the game.
You are right to upgrade your planet population ASAP. This will be your main source of income throughout the game, so upgrade your planets quickly and often after you grab them. If you don't you can actually end up with negative income...
You want to build ships at least to the first fleet cap as soon as you have colonized your first asteroid. Keep expanding, but make sure you have a group of 10 frigates or so to back you up in case you get attacked.
Chose one tree of research, economy or military, to focus on early, and work to get the benefits of that tree before moving to something else (so if you go econ, get trade ports before you go military...if you go military, upgrade to a higher ship type or two before you look at econ)
This should get you beyond 5 planets in 90 minutes, but if you run into trouble let us know