Well, I make a ton of money gathering:
1. Level up all gatherers (takes time and a few Netflix series)
2. Adamantite Ore with King's Yield II (that's 25/half hour if you are lucky) OR fish up big fish and sell them to starving CUL OR ....I don't know I hate botanist I literally only use it for scrips
3. ???
4. Profit
You make more money if you craft guaranteed but... the gil investment early on is higher. But the returns are better.
Edit:
Oh also
Never use materia, always sell it for fat stacks of gil.