Crafting will save you some expenses, but gathering is the one that will make you some money (although you have to enjoy it and can't just do it for the money).

Treasure hunting (comes from gathering classes 40+) is a great way to make some quick gil, just like the beastmen dailies (42+) and the Roulette.

Biggest way to increase your wealth? Stop teleporting everywhere. It's not free and ads up to a LOT of wasted gil. Learn to use your mount(s) and the ferries/airships to cut down on teleporting fees.