I never did that blackjack game, i dont like that game xD

Necron is pretty frikkin easy IF you meet the right criteria:
1. make sure you're protected against most, if not all, bad statuses
2. make sure all your characters are at least mid 50's, although it's certainly much easier if you're in your 60's
3. screw eiko's Holy, its weak, and screw the dark matter items. get everyone armour or some type of item that either guards or absorbs (absorb is definitely better) dark attacks, and let vivi use Doomsday every turn
4. put Zidane on high tide...with his trance doing 9999 each time he uses it and Vivi's doomsday doing 9999, necron will go down fast