Drops from luna gold players increases this margin a bit.
The only consistent source of semi-large quantities of gold, is Grinding, for hours on end at certain areas. Ogres, Dark Gate Guards, and a few other areas give enough gold via just gold dropped by the monsters to give you a mile an hour, at the LEAST, and napping the common drops from luna gold players increases this margin a bit. Every other gold source, from fishing to rare hunting to setting up a shop and hoping your items attract a buyer, is lucrative only in relation to your luck. Luck isn't consistent. The majority of the population on Luna is most likely going to have more bad days or "average" days than they will good days, luck-wise.