When you need Gil (or levels, for that matter), skeletons are your friends. Go back to Bhujerba--one of the bridges in the Lhusu Mines spawns huge numbers of skeletons. Chain them, but don't pick up any loot until they drop the big gold medallion-type things instead of the little bags. (It'll happen faster if you refrain from picking up any loot.) They'll drop Bone Fragments that sell for a decent amount of money, especially for this early in the game.

I also agree about the Hunts - they're good if you need a quick infusion of cash; make sure you steal from the marks before you kill them, though. You can get some decent loot that way too. I hope you're talking to Montblanc whenever you drop in Rabanastre - he rewards you with Gil and items for defeating bosses.

One thing to keep in mind is that you can often get equipment through means other than the normal shops. Some can be acquired through the Bazaar if you sell them certain Loot and if you're flat broke and desperate for new gear, you can chain certain monsters in hopes of them dropping equipment. It takes some patience and more than a bit of luck, but on the bright side you'll also get more exp and loot you can sell to make more Gil to buy more gear, so the only real downside is the time it takes to do it.

Unfortunately without knowing exactly what gear you have I can't really tell you where/how to find better stuff...if you could give me a list of exactly what equipment you have I'd be able to give you more specific advise.

Gambits can be found in Gambit shops, they usually aren't too expensive so you should try to buy in bulk whenever possible. A lot of Gambits can also be found in chests when you're out and about in the world. It's still fairly early in the game and you probably won't have a lot of the more useful gambits, so you may have to cast magic manually for the time being.

~DragonHeart~