You should draw all you can to start junctioning to your stats as soon as you can. Once you get the higher level magic, you can always discard the weaker versions at that point to make room when you need it. You can discard an entire stack of 100 spells at once so there's really no reason to worry about loading up on weak stuff for later progression. You can also shuffle magic to other characters so if you want to keep a certain magic for certain circumstances, shuffle it to a character not in your active party.
Thanks for the tip! With regards to just leveling up then, what is the deal there-it's frowned upon to do any serious grinding? Last time I played the game near the end (somewhere around the end of disc 3) and I was around level 23. Good? Bad?
Cheers.