Earn some more gil and buy a bunch of Phoenix Downs from either Nalbina or  Migelo's in Rabanastre (if you've done the Sunstone quest) to prepare for some serious leveling. Once you have a good stash, head over to the Westersand and  beat yourself up until your HP drops below 10%. Once you're there, go to the Corridor of Sand.

Dustia, a rare monster, will show up. It is an undead monster, so a Phoenix  Down will kill it in one shot. It is also a teleporting monster, which means  that if you kill it but leave the area before the Exp/LP totals show up, it  will respawn once you reenter the area. You get about 1100 Exp per Dustia. This translates to about 20 levels in around an hour, less if you get good at it. What's also good about this method is that you effectively build up a chain and  can stand to make some serious gil. Practice picking up the loot and exiting  without breaking your chain and you'll be able to pick up a lot of Book of Orgains, which you'll be able to sell for a lot of cash. By the way, I don't take credit for this method.

Remember, whenever you want to leave and save before heading back for more,  you have to be below 10% of your max HP before Dustia will spawn.