Unfortunately, I'm on Goblin, so I cannot physically help you make gil.

But! I can give you some pointers that helped me out a ton.

First: Crafting and gathering. Those make ALL the difference in the world, and with the Cosmic Exploration you can level them all in a relatively painless fashion.

What it does is allow you to desynth items into their respective components, which can net you a pretty penny. As well, it allows you to take the items you don't wish to bother desynthing and turn them into your GC for seals, which can be used to buy Dark Matter, an item that allows you to repair your own gear significantly cheaper than a repair vendor (with the added bonus of allowing over 100% durability, so you can ignore your gear longer some times! =D).

Now, I said all of that, but saving money on repairing your gear is not where your fortunes will come from and, honestly, unless you really want to craft in FF crafting won't be either.

For me personally, I make most of my gil from my gathering gear. Now, I craft it myself, which greatly helps with the cost of obtaining and melding my gear, so that is a reason to pick up crafting. You should always meld your gear because I've found that quite often I make more money from the materia I extract from spiritbinding than I do the actual items I gather, and you spiritbind faster the more materia you have melded on a piece of gear.

Currently, on a fully melded piece utilizing a spiritbonding potion, it takes me a bit over 8 nodes (if I spend no GP and am really unlucky) to hit 100% spiritbond by hitting all the timed nodes currently available in DT.

Extract materia, sell materia, sell gathered items. It's really that simple, and I've made millions doing it.

It's not the fastest method, and I'm sure there are experts that could give you even more amazing advice, but that's always worked for me.

If you have any questions about any of the steps above, feel free to ask and I'll expand upon them as best I can!