If you're worried about magic for your party, remember that all though most of them can learn magic, only a few are really talented at it to start off (the esper system can fix this issue) Terra, Celes, Edgar, Mog, Stago, and Relm all have natural talent for magic. Teach healing spells to everyone but if you're worried about grinding focus on these character when it comes to teaching support and offensive spells.

As the game progresses you start to to get espers that teach low level magic fairly quickly so its not too difficult to teach everyone, but in my experience, half the cast really doesn't need it.Mog, Cyan, Edgar, Sabin, and Setzer can easily hold their own without magic.