Well, I usually have full enemy skill materia on everyone, and then I'll customise what role they play (for instance, final attack > phoenix on someone). I play with Cloud, Barret and Tifa so I always make sure Barret has materia that has the most amount of AP for his final weapon.

As long as everyone had enemy skill, the game was easy enough (you had white wind that would heal health and ailments fully, big guard and plenty of damage spells).