Have Vivi, Steiner, Eiko and Zidane:

Have Shadow absorbing armor: Vivi's Doomsday will heal you whenever you want. Equip Return Magic to Vivi, he can cast back Doomsday to double-heal your party (sometimes Ozma absorb it but it's not a disadvantages!). Eiko should use Curaga to the party anytim even if the party in full HP, also do use Full-Life, don't bother using Elixir and Holy though. Steiner Shock will always hit for 9999 while Zidane mug Ozma to get nifty things.

If you want to dig Chocograph, do it after you obtained Hilda Garde 3: You should few Ultimate Weapon, helpful item and great armor. This will make things in Terra a lot more easier.