Goliath

Best way if you want it quickly is to hoard about 300 gems/crystals that you can harvest just about anywhere and sell that to a vendor. You will be filthy rich in no time now buy them back and them again. Repeat until the Achievement pops then reload your safe if the auto save wasn't to recent to undo all of the nonsense. Or just leave it as is if the Save is overwritten as money in this game is worthless and comes by so quickly with the trick just shown.