Um, are you sure you have the right game? There are no infantry in Sins of a Solar Empire, just ships. But if you really do mean this, try this.

1. Always buy the first two (one for asteroids) population upgrades on new planets ASAP. The surest way to kill your economy is to fail to do this.

2. Acquire nearby "neutral" extractors in nearby asteroid fields, plasma storms etc. to boost your metal/crystal income. They are free and provide a little better income that regular buildable extractors.

3. Be careful what you research. While some items like terran planet population bonuses pay for themselves rather quickly, others do not, and its usually better to wait researching them until you're in a better position.

4. Don't overinvest in trade ports or refineries. The best way to make money in Sins is to acquire new planets. Don't start putting trade ports down until A. Your military is strong enough to protect them and B. You can no longer easily expand to nearby planets.

Thats about the best general information I can think of. With improved cash flow, you'll naturally be able to build more and better ships. If you have some more specific questions feel free to ask.

You should at least max out your opening slots, i.e. build until you can't build anymore.  Once your economy gets good enough, you will want to continuously "fleet up" as funds permit.

heres a tip, upgrade ur civillian infastucture. that will boost your economy. also resaerch bettter resource gathering techs in the harmony tree. after you have a strong economy and get lots of high power ships id say just attack fast so ur enemy cant react in time.

resource gathering techs.... idk really, ive only been here awhile, but each level of upgrade only increases your income by .1, so total you can only get a .6 upgrade. and they are real expensive so it takes awhile to pay itself back off, much less start earning you profit.

now, if you have ALOT of extractors, then this is actually a better thing, because it increases each extractor by 7% or whatever each time. so more-extractors=more cash

5 days arrived and too new to know all the tricks, in the first few replays I've watched, I've seen players use what appear to be some clever micro tricks to clear efficiently.  I believe, for instance, that several colonizer caps have speed advantages that help clear more efficiently if you move the cap about, rather than just jump to the planet and let it sit there fighting.

I have to rewatch closer and figure out if that if actually a pure speed and range of fire thing, or better leveraged the bomber strikecraft the cap had, or both, or etc.  Once you get the basics down though, there are definately some colonization micro tricks for modest speed or health bumps.

-evoke

You can only claim neutral extractors in uncolonizable gravity wells.  If the gravity well is colonizable, you must colonize the planet then build extractors there.  Otherwise, you should be able to capture them with a colony frigate (it's hte second ability, the one that costs 40 antimatter).  If you're playing Vasari, you use your scouts instead of colony frigates.

Neutral extractors only appear in uncolonizable gravity wells. They also have the invulnerability buff applied to them at all times. If that was indeed the kind of extractor you were trying to capture with a colony frigate's crew extraction (or what it is called, the one besided colonize) ability, I don't know. Can you post a screen shot?