For more cargo, buy at least one ton of rubbish and go to a system where you won`t be caught for dumping it. Then go to the cargo screen and click a bit below the rubbish box. You should notice that the remaining cargo has gone up but the amount of rubbish has stayed the same. Keep doing this and soon you`ll have enough cargo space to get a large plasma accelerator. If you do this in a small ship, eventually you`ll be able to buy a class 7 hyperdrive and jump a long way across the galaxy with somewhere around 50 tons of fuel.