Teaching other characters is fine with us! If the character learning has no canonical magical aptitude, by precedent we've established that they can buy 'innate' magical power with 500 coins. Though a high investment cost, these characters can then gain magical spells on their own, without the need to spend on additional rewards. And in general, we would like them to learn at a reasonable rate, start at fairly weak levels, and take time to master new spells.

Please let us know if you have any additional questions!