Thanks! I had a couple star patterns sketched out too, but a) they were cliche and b) they didn't quite work since I had to visualize that holy & gravity were rare forms of magic, so I went with a color wheel idea. One of the sketches was a 5-point star with some kind of extension, so each elemental type had a matching pair:
Water > Ice, Shadow > Gravity, Fire > Lightning, Cure > Holy, Air > Earth
The only one that didn't make sense was Air > Earth, which are considered opposing spells in the game so that idea was scrapped. I also considered adding in 2 more spell types (sand & crystal) with a 6 point star but that was quickly scrapped too. I still may use crystal as a true non-elemental (center icon) magic type. With sand, I think there's just the "Sand Grip" and "Sandstorm" spells, so I justify those in that they use both earth & air qualities. I'm planning on throwing in some mixed spells like that anyway that either characters can learn from skill books, or are only used by enemies.