How to get rich reasonably quick?

[Disembodied]

You need to do the bulk cargo runs to build up your reputation to the point where you get the sweet deals – so yes, you really need a big cargo hold at first. You can always trade back to a zippy fighting ship once the precious commodities come on line (although you'll have to keep your reputation high to keep the jobs coming in; reputation declines over time if you're not making deliveries). And as you increase your rank in Random Hits (and, I think, in the Navy too) you'll get offered more lucrative missions as well.

[Zanasj]

With Cobra's cargo hold, it's sometimes hard to find contracts to increase reputation. Speaking of which, do the UPS missions add to only UPS rep, or bulk cargo rep too? It could be a coincidence, but after I finished a couple of UPS runs, I got suddenly offered my first gem delivery contract.

With my old pilot, I upgraded to from Cobby to PCC, and later to SuperCobra (a good ship, but the maintenance costs are a drag). With my new pilot, I bought a Josher, just to try it out. Now I'm hoping to get money to buy e.g. Terrapin or Griffin 2.

If you feel like running booze and buying (more) valuables, buy a rock hermit locator.