If you want to know who to ignore: Umaro, because he's constantly in berserk mode. Gau, if you're a completionist, because getting all his Rage abilities can be tedious. Cyan, because for a samurai/knight, his attacks can be underwhelming. W/ so many good magic users (see next paragraph) Strago & Relm kind of get lost in the mix.

I suggest going w/ the Figaro Bros. early on. Edgar is very powerful w/ his tools & Sabin is a good damage dealer (also in the 2nd part of the game, he's one of the few available characters early on). Celes & Terra are both very well rounded, w/ swords & magics.