Ok I got both cloud and Aerith new limits and we both level 24 . I improved my atb and first strike materias to help Aerith get a quicker start. With her current weapon stats also she’s kind of a beast with launching spellsYou should be good because I didn’t even do the coliseum after the boss fight. I don't remember what level I was, but I did pretty well for the rest of the game.
I would suggest to get HP ups and maybe MP ups. Those helped me a lot, but I used them real late in the game.