I've been playing for about 4-5 months and have 50 million just doing roulette, dungeons, raids, trials and nothing else. I have no crafting jobs leveled. I only spend gil on raid consumables so I don't need much to survive. So you can just do those daily roulette and make a lot of gil. If you want to be filthy rich with like 300 million or more, a lot of those players either craft or have been playing for a long time.