Every mysticism spell I've come across requires at least a 25 in the skill in order to be used; however, my mysticism is only 12. I'd like to be able to create a minor spell for training up the ability, but the spell-making table won't allow me to use any spell effect that I can't already cast. How or where do I raise my mysticism enough to be able to practice on my own, and is it possible to do in a way that doesn't cost a ton of money?
The cheapest mysticism spell that requires no skills to cast is Minor Life Detection. See if you can find yourself a copy of this spell. The shopkeepers that sell them are: Alves Uvenim, Calindil, Edgar Vautrine, and Ita Rienus.
Once you get it, if you already have access to the spell making table, then you can use it to make a even cheaper version that lasts 1 second so you can spam it over and over.