Ignore Admin Cap. If it is actually hurting you, you are winning.
Don't worry about specialization. Once you get the basics, it is a way to get a bit more efficient. It is not necessary, ever. Your capital gets +3% to everything, so when in doubt, build it there.
If you think you can colonize something green, you probably should. If it is yellow, do it, but don't grow it; resettle them to your capital until that is clearly a bad idea.
Planets should have either 1 pop, 5 pop, or 10+ pop. All other numbers are bad juju and should only be allowed temporarily, and if you have people you don't need in your capital, feel free to resettle them to fix it.
If you need stuff, buy it. If you are broke, sell food. If you are not sure what to do, make more food. If your selling so much food the market is not recovering, make minerals. Don't sell minerals if you can avoid it; make them into CG or Alloys (50 / 50 is fine for a long time) before you sell them. Only sell those if you have to. If you have too many CG, build labs. If you have too many Alloys, make ships.
If your not sure how many ships you should have, take the game years since you started and divide it by 3 and add 3. That is about right until you turn up the difficulty a lot and even then it is often much cheaper to give your neighbors food then worry about ships.
Ignore space mines/labs that aren't energy or at least a 3 until you have done everything else you can think to do and have minerals sitting around in piles. They are a trap. Except the alloy ones/special resources. Get those.
If you ignore "trade", it will mostly ignore you, and that is ok. You don't need it. Figure it out when your wondering if you should raise the difficulty level.
If your wondering about Traits, take Agrarian. You can't go wrong with it. It is like jeans; it goes with everything.
Don't fret over Ethics. They are all pretty equal and there mostly for flavor. Unless you are sure, don't go fanatic anything. It is often annoying. Choosing based on RP is as about as good as anything.
Civics, be a little more careful, but don't stress it. If it starts with "A", it is a good pick. If you ethics don't let you take any civics that start with "A", consider changing your ethics.
Unless it really floats your boat for RP reasons, don't play Democratic until you are at the point where getting a little free unity seems like it might be worth extra micro and annoyance.
If you feel like the micro gets silly as you get bigger, your not alone. That is normal and it is ok. Just make sure your Empire is too big to fail by the point you can't take it any more and ignore any level of micro that makes you not enjoy the game.