What party do you normally use? A party tha you pick for any situation. Be it Necron, or fighting your way through Mt. Gulug.
Bear this in mind, you do not necessarily have to include Zidane (as if you were fighting Necron). Also, assume that every character has all their moves, and are on the same level.
I would use Amarant, Vivi, Steiner, and Quina.
Quina and Amarant can adapt to any situation, and so go in any of my lineups.
Amarant's curse combines brilliantly with Vivi's black magic and Steiner's sword magic. He only has to use it once, and then he can assist them with his attacks as well.
Quina can heal, even if everyone has auto reflect equipped. Which, quite simply, rules. Amarant can heal also, and since this is a heavy magic party, he can also recover those essential Magic points.
Steiner and Amarant are perfect for fighting enemies that are not affected much by magic.
Vivi can take on any adversary and win, provided you realise your opponents weaknesses. Plus, with Shadow absorbing armour, Doomsday heals every turn.
Steiner and Amarant have tons of HP, meaning they are very difficult to kill.
Basically, this is the best all round party in the game, it's only weakness is against enemies that can do exceptionally high damage, because the 'healers' in the group don't recover as much as Dagger or Eiko.