The Civilian Cruiser and Civilian Transport should be the top two ships available in the design screen. You may have an older version of P&N, though.
Using units can help a lot; no maintenance on them.
You definitely won't be able to build many ships, though, and the ships you capture will be pricey... scrap or analyse them as soon as possible.
One of the best things you can do is capture a planet with troops. If it is a high mineral value world, the AI will probably have built miners on it, and you'll be instantly rolling in resources from your slaves.
The AI will quickly come to glass it though, so loot then pilliage and then run away
And do throw the cheap tricks:
One or two weapon-destroying mines can cripple enemy targets so you can capture them without resistance.