Start of battle have Rikku mix Hyper Mighty G for Protect, Shell, Regen, Auto Life, and 5x Cheer, Focus, Luck, Aim, and Reflex. Have defense about 165 but not to high so all 3 characters will automatically have od refilled after each Hydraulic Press. Afterwards use Quick Hit followed Mega-Potion each turn because unless your defenses are at 255 Greater Spere can cause anywhere from 2000 to 6000 damage each turn with Ultima/ normal attack. Also, make sure you are causing anywhere form 60000 to 99999 damage each turn or else it will be a really long battle. Also, for the strength, magic, defense, etc. spheres battle the species creations. Of course for Luck and Fortune spheres you'll need to battle Earth Eater and Greater Sphere.