Magic in my worldbuilding is publicly available knowledge but not many people have the aptitude for it! Theres of course exceptions to every rule, but the trend in my worldbuilding is that species with a certain rarity, mythical and legendary creatures most of all, are incredibly magically potent by average! And the type of magic you can most easily use is determined by a kind of public unconscious, the folklore, traditions and religious iconography of your species! So as a little example, Pas is a relatively common sheep, they dont have a magical bone in their body! but if they could do magic they'd most naturally be able to cast spells relating to sleep and dreaming because those are common associations with sheep in the public unconcious!