Its very easy to get chains higher that 50 or so. Right after Lamont joins your party, go into the Luhusu mines and on the second bridge, you can get a chain of at least 30 or so, then when the spawns start to run out, zone south, then past to the first bridge, then return. I got to level 17 with everyone like this, in about two hours. Lamont in your party helps a great deal, because he has those unlimited potions. My chain record there is 243. They also drop done fragments, which, by a 170 chain, are near to 99. A stack of these sells for around 20,000 gil. Average or 98exp per skeleton with Lamont in the party.

The next easiest place to level up is on the platforms in the Ogir-Yensa Sandsea. If you run from the Pineapple king and the Yensa, concentrating solely on the Urutan-Yensa, you can get a rather large chain. This is an excellent place to level up in, because it is very large, and there are gate crystals on each side of the area.

These two methods are what got all of my characters at least two quickenings each, with two having three, and enough gil to fund the entire Archadian Empire, or their downfall, if you will.