You have a cool game, Userfag. I can easily envision a parasitic leech stealing your idea and turning it into "Spell RNG" or some other cash-grab bullshit. Maybe that parasitic leech will be me, you never know! With that being said, I have a little feedback.
Change the way you detect spells in messages. I assume you're just using string.find() and because of that, if I tell someone "try casting [SPELL]" it will cast that spell, which could be annoying. It will also cast a spell if I say a word which contains that spell. For example, 'Error' will cast 'erro.' I understand this is a little nitpicky, but it's the small things like this that can really make-or-break a game. Even if your average player won't complain about stuff like this, they'll notice it all the same.
You should also remember to make the spellbook tool (and all the parts inside of it) CanCollide/CanTouch FALSE and Massless TRUE. I noticed that the spellbook also functions as an extension of your character's hitbox. Turning CanTouch off as I just suggested will fix this issue too.
Ask me if you ever need help with datastores (or anything else, I suppose) once you inevitably get to them. Most beginner developers (myself included) lose their shit when they try to create datastores, but I can promise that they're really not that complicated.

It is fucking impossible to get the 'decipio' spell to go where you want it to go, by the way. Picture related took me a very long time to construct.