By abusing skills that can cause massive damage without costing a lot of Mp, like Quina's Limit Glove. 9999 damage for only 10 Mp. Dragons Crest can also cause 9999 damage for only 16 Mp, and Thievery can cause 9999 damage for 8 Mp. Early bosses can be dealt with in other ways, but later bosses require these skills. Dragon's Crest requires kills to power up, but I used Zombie to get around experience when powering itOriginally Posted by Sain Cai
Bosses don't give exp in FFIX. There are a few forced non-boss encounters that do, but using Stop/Petrify will end a fight without exp being given, and later on you can just give everyone Virus and never have to worry about exp again.
There are those three battles in Pandemonium where the monsters are immune to every status abnormality. At that point a few characters have to gain exp, but not all. You can still beat the game with a party of four Lv.1 characters.