if you go through the game without running from battles (which is what i always do on FF.) your usually at a comfortable level that will suit whatever boss you come to. if you do this you may have a few difficulties but nothing that cant be solved by better strategies and slight leveling. if you do this you should end up at about level 50 before the end of the game. you can beat the first disk by being about level 25 ish (maybe a little lower.) im sure theres a guide on gameFaQs that gives you reccomended levels.