I like to Mix :
My spellcaster - Normally Aeris - or tifa after disk one
Restore with all, then equip a load of magic materia in the other slots
My Warrior - Cloud
Restore with all *again* 4Xcut and the standard magic materia with 3 HP Plus in there too,
Summoner - Barret
As many summons as possible, enemy skill materia and about 2 MP plus materia and 3 HP plus materia
always seemed to work out for me
My spellcaster - Normally Aeris - or tifa after disk one
Restore with all, then equip a load of magic materia in the other slots
My Warrior - Cloud
Restore with all *again* 4Xcut and the standard magic materia with 3 HP Plus in there too,
Summoner - Barret
As many summons as possible, enemy skill materia and about 2 MP plus materia and 3 HP plus materia
always seemed to work out for me