You could try opening a 'Mint' corp. Seriously, I think you can sell Countries/CEOs. Or products in space but I believe that means an initial GC investment. Not much help, huh. Oh, yeah you can win awards for high rankings. Try buying them over the forums @ less than GM prices. Good luck.
Space and GC market require being a premium member, along with nukes. If you are looking for more gold coins than you have to add to rankings. I dont even think freemium members can sell countries, corps, or enterprises.