I'm only level 27 and I am making quite a lot of gil. for example last night I put about an hours worth of harvesting stuff on the market board and wake up this morning and its all gone and my retainer has 30000 gil waiting for me. iv found logs sell really well and there's always shards and crystals . they go straight away most of the time. I don't do any crafting at the present time so everything I harvest I sell