What else should I farm for data battles?

So I have a friend playing the series for first time and I want him to do secret bosses data battles Sephirot etc.

Im on a save game from my profile since making him fight them without maxing out or making him farm everything would make him bored.

Long ago since I maxxed everything in this game and forgot about most things, I did all Drive forms, summons and lvl 99.

Artema weapon is something I know but im still in doubt since I feel decisive pumpkin is just better.

So anything im missing? Probably from the synthesis moguri shop, anything like accesories or defensive I should do?

Playing on critical btw, so even tho he is playing in max difficulty I want to make the secret bosses a little bit more comfy and accesible for him so he may enjoy them more without frustation.

Thanks!!!!