My personal method for getting money relatively easily and quick is mining Diabosite until you get tired and selling it to the blacksmith, once it's unlocked.
Another moneymaking tip is that eventually, you get the ability to help out Bernard for the entire day if you get there early enough, and that gets you 100 coins without much fuss.
I had no idea the money happened every time you do the event and now I feel dumb for not using that to get money when I needed potions and shit for..... Every boss ever....
