i would advise trading in rares until you can aford a 200 tonner, then find a route were you make 1k per ton too and from. There are some systems that export slaves and import metals, and vice versa about 20ly away from each other, finding them can be tricky though. Although the system im using atm does not import slaves but still has a medium demand for them, while supplying the metal needed for the trip back to buy slaves.