Rinoa sucks
Do not try and level up. Monsters level up with you and gain more magic. Now, while this could mean that you can draw higher magic from them, it's just easier to take it from The Islands Closest To Heaven and Hell. So, do not fight random encounters if you can avoid it. Just learn enc-half (followed by enc-none) as fast as you can. It rocks when you fight the end boss and it doesn't even have Curaga. *grins*
There is a trick! And it is a good one that isn't in the strategy guide (well there are a few not in there). When you are in Dollet as Seifer, Zell, and Squall kill off Zell and Squall. Ask forgiveness of them of course cause they are beautiful! =) Anyway, junction all your GF's to Seifer. Have him draw magic and just kill soldiers. After a while, the soldiers will gain cura, thundara, etc. Draw those too. Make sure you give any excess magic to Zell and Squall, so that you can have the maximum amount of this magic. Keep fighting. Your GF's should be learning almost everything by the time you get curaga,thundaga, etc. from the soldiers. When Seifer leaves your party, all your enemies are back to being the level they were in the beginning and now all your GF's are already trained. Hooplah!