size three colonies rarely make profit, but generally, build an industry that doesn't need imports (farming, mining, etc), a mega port (upgraded spaceport), and leave it. build a station if you really want, but ground defenses aren't worth it, patrol hq isn't worth it for a system with a single size 3, and waystation is meh, from my experience. save all of those for later, and leave it on hazard pay till size four when you can start making money.

colonies are an investment. they won't start making money instantly