I need a few suggestions.

I'm on the Song of Nephilim, and Shion is only level 23, and I think chaos and KOS-MOS are about 28, and I'm having trouble even surviving the on-screen enemies in the second tower. I know I need to level up, but my characters are even dying just trying to fight in there. The place on the EVS with the enemies that give the most experience is the KOS-MOS simulator on Miltia, but even then they don't give enough to level up at a good rate.