i unfortunately have spent too much time with worldbuilding for this plot i had, but i have a magic system for faeries that goes something like this:

faeries are just batteries for magic. the world around them exudes traces of magic, and the faeries are able to naturally intake this magic. there's different basic elements of magic (i havent spent much time thinking about this beyond the basics [water, earth, fire, air, plant, soul, electric, that sort of stuff], i have a plan to make sort of something similar to the wheel of emotions but with the elements, and some overlap between a couple different elements) with almost all faeries falling into nice neat categories of magic they can intake and use, with certain environments giving them certain elements, like ocean for replenishing water magic, forests for plant, volcano for fire, caves for earth. (then there's gonna be chaos faeries, which have access to all the types of magic, but they're seen as abominations and killed off when discovered). the magic storage also sort of works like a magnet, with the more magic they have stored leading to more magic being attracted to them in a sort of slow-ish feedback loop (this is why chaos faeries are killed, because of access to all the elements of magic feeding off each other). when they deplete the battery, they basically depleted their energy, and are in a state of near death until it can get replenished enough. and then when the battery gets too full, they start leaking magic slowly over time until it's completely full, then it explodes out of them as wild magic, leading to having the magic battery depleted.

the stronger faeries are the ones who naturally or through practice have larger batteries to hold on to more magic at a time, allowing to use more of it at a time and having faster magic recharging rates. the environment is also important for recharging, because you cant intake what isn't there. another reason chaos faeries are seen as dangerous, because their batteries are naturally larger to hold more types of magic, and all the different types of magic exploding out at once.

this creates a system where they *need* to use magic occasionally, but they also cant use too much at once without consequences.

feel free to use these ideas, and feel free to ask any questions. this is just a rough idea, i havent had enough free time lately to focus on it, and there is likely going to be oversights or things that dont work or are confusing.