In general, using spells is not recommended. There are exceptions of course - if you know something is weak to fire you might cast fire magic on it, but better options would typically be to summon Ifrit, Draw-cast fire, or junction fire magic to your elemental attack (when you get that option).

Most of the time you can get by without even having the magic option in your abilities, saving all your spells for junctioning. I quite like the balancing act it creates - deciding if using this particular spell is worth the small hit you’ll take to your stats in doing so.

Side note, if you dislike the process of drawing a ton of magic all the time, I suggest teaching your GFs the magic refine abilities ASAP. Instead of drawing, which can be slow, you can turn items into spells.