My highest chain was about 250 in the mines with those skeletons. I actually found them a great way to level up and get money. Easy to kill too. With the right gambits, I can just move from area to area and let the characters do their stuff while I can do other things elsewhere xD
It was so fun, lol. Penelo just shot them with a bow repeatedly, and I ended up at level 11. well, and I had about 10000 gil to play with!