Slow resources

Orbital Refineries are a bad deal in most cases.  Trade ports are a far better use of your time and efforts.  In most cases, it's better to build a trade port to earn extra credits and then spend the excess on the black market.  It's only late game when you have lots of extractor upgrades that refineries become useful, and even then I almost always place them on planets that would break my trade chain.

One thing you have to remember to do is upgrade your planet population infrastructure.  Population infrastruture increases the maximum population of a planet, allowing more people to live there and generate tax revenue for you.  As well, if your population infrastructure is too low, you pay underdevelopment tax, so it's a good idea to get rid of that as soon as possible.

Typically, planets are a poor source of metal and crystal, their extractors producing very small amounts.  If you have high upkeep levels (fleet research reduces their efficiency, unfortunately), this can reduce your incomes of raw materials to very low levels.  However, neutral extractors in asteroid fields or other uncolonizable systems will produce far more than their planetary equivalents.  These are the important ones to capture, and these are the ones you want to build refineries adjacent to.  If you're on a map with few or no neutral extractors, you're basically forced to use the black market because it's completely infeasible to get enough metal and crystal through extraction alone.

sure thanks man.. that helps... so im guessing that i should find asteriod planets and build extractors there rather than capturing the asteroid??

One mistake i did recently is to upgrade my fleet capacity, and so increase high resources penality. My advice is to keep a little fleet at the beginning, and increase the fleet technology when you really need it. It can help

I didn't say not to capture asteroids.  Their metal extractors may not be as useful as the ones in neutral territory (like asteroid fields), but they're still important assets and well worth the cost to acquire.  As well, you can build structures in these systems once you own them, including trade ports, repair bays, and research labs.  The problem is that a lot of players ignore asteroid fields outright.  What I'm saying is to give them a fair priority, but not reverse the problem and ignore colonies outright! 

As far as fleet capacity goes, you purchase it as you need it.  Ensure when you purchase the next level that you have enough money stockpiled to immediately produce a large number of units so that you put the higher fleet level to immediate use.  There's nothing worse than upgrading your fleet capacity, then not using it for several minutes because you couldn't afford to make new units.

also, allegiance becomes a big factor once your empire grows. don't underestimate the effectiveness of culture boni

Keep in mind uncolonizable planets don't have loyalty, and therefore always function at 100%.