I usually give 1 person the All+Restore combo, as well as the full line of Heal+Revive set, and some of the status effects that reverse each other, such as Transform, as well as Enemy skill to give them a wide range of offensive spells without using too much materia spot

Then I have 1 person that has restore, and an arrangement of attack+all spells, potentially a summon too (for the +mag boost), this is my Nuker for when the occasion calls for

The other person, usually cloud, doesnt get much materia. He'll get Restore, and maybe 1 or 2 attack spells so he has something, but otherwise I keep him light so his melee stats arent gimped too much