I'd prefer something alittle bit more thematic. Much like acquiring GEO, I'd rather go to a ??? and pop and appropriate NM elemental type to kill. Not for all the spells but some of them. The drop would include a geo-scroll

Alternatively, an certain % of "knowledge" can be gain during weather effects and/or enviorments. Killing X amont of mobs or buffin X amount of times during storms can unlocking level appropriate spells and spelltypes.

For example, accuracy (is lightening based). During lightening storms...casting "lightening type" spells increase the % rating.

A final alternate method is the "caring method". Feeding a Lupons either crystals, feedwell orbs(synergy items), or the trial items(can't think of them atm)...gains a certain affinity. Think affinity level. Each elemental affinity level can coincide with the level of the spell. Example. a lvl 5 spells require you feed Lupon to affinity level 5.
As an aside. Affinity level could have an affect on the effect of the lupons spell directly.

just ideas I'll pullling from my butt.