My first FF was FFIX.
I fought Necron with lvls:
Amarant: 44
Steiner:42
Freya:45
Zidane: 48
All my characters had crap weapons as it was my first RPG. I didnt know how to equip summons, or get magic, abilitys etc.(I lost the manual so when equipping I always did optimise and hoped for the best)
Somehow after 6 goes by fluke I won. (Discounting a few times I failed to reach Necron by dying to Kuja)I only used attack or items (and Jump for Freya). I remember the battle lasting for ages, since I did tiny damage, and luckily my Freya jump missed all Necrons major attacks. - So even if your partys rubbish, try loads of times and your bound to suceed.

When I replayed the game I just used shock, ark with pumice peice and regen....easy.