This trick requires ATLEAT level 2 lightning and massive amounts of Will Potions.

Go to the Greatwood Caves (The area leading you to the Hobbe Cave). You should fight several monsters, then make your way into the Hobbe Cave. Continually use the lightning to hit two enemies. This will drastically increase your magic EXP. Once you have around 18K experience for magic and general combined, SPEND IT ON LIGHTNING. Common sense, if something works, it'll work even better if you upgrade it! Now, you have a stronger lightning that hits 3 foes, simultaneously! Get 48,000 experience (It may sound liek a lot, but it comes surpriseingly quick), and upgrade to Master Lightning. Now, zap the little buggers all day long and upgrade any magic.

Note- Every room full of Hobbes will give you around 8,000 experience if you kill them all with lightning.