not sure if this will help but never buy gold with plat, its a waste buy pots/idools/elixers/ect. and sell to other players you will make way more off that, Another tip is if your like me i only buy plat every once in awhile, i make gold from non-stop grinding or lvl up and get in a boss group and sell the drops. if theese tips dont help you, ill leave you with my best money making tip of all.. kill fal or brut, get a dd and sell, theyll always be worth something. dds pretty much fund my pot abuse
hope this advise helps ya