Regular hunting and doing quests can get you along just fine. Purchasing items, especially the enchanted gears, from users are waste of money because most of the sellers factors in the cost of Enchant Stone and the basic value of the gears. I'm sure that there are quite a few number of players that has already accumulated billions of gold and much more money circulating around the market in terms of items and gears.
10-15 million is plenty up to level 50~60's to purchase items that you think are absolutely necessary to finish the quests and such. Beyond that... purchasing Growth Vials, variation of gears, and buying large quantities of crystals are just a luxury... although you should at least max out Growth Vials [Mid] for your mercenaries.
Th easiest way to earn gold is probably Crystal farming, redo mercenary quests (which takes a long time and rapes your stamina), or exchange books with Goncourt (I do this).
Good taste is a dying breed.