Tales and Chronicles
Jewel of the North, formerly know as vincegetorix
If you go with only one spell list, which is a superb option to let players decide just what kind of casters they are in addition to the origin of their spells, I'd maybe give a look at Beyond the Wall OSR rpg (it also has only 3 classes)
In short, spell auto-scale with the characters level, much like in previous editions, but there's no spell levels. All spells are close to 1st or 2nd level in D&D parlance, but they scale automatically, no upcasting necessary. You get a specific number of cast per day, no need to have slots of different levels since they are all the same.
In addition, you have rituals that are gated by the caster level and are no available to cast with slots.
It makes a simple that is quite simple to learn yet is very evocative and makes magic powerful, balanced and feel like actual magic.
Its worth a look.
In short, spell auto-scale with the characters level, much like in previous editions, but there's no spell levels. All spells are close to 1st or 2nd level in D&D parlance, but they scale automatically, no upcasting necessary. You get a specific number of cast per day, no need to have slots of different levels since they are all the same.
In addition, you have rituals that are gated by the caster level and are no available to cast with slots.
It makes a simple that is quite simple to learn yet is very evocative and makes magic powerful, balanced and feel like actual magic.
Its worth a look.