I'm just about to head into Antlion's Cave for the Sand Ruby.

I got this far my first time but I was hurting like hell because of no potions and no MP - didn't realise Edward's Heal ability wastes potions (oh Eru, he's like Larsa in that repect!). Hopefully I'll do better this time since I have a better potion supply and I know how to hit multiple targets with spells.