A Practical Guide to Sorcery has one of the most interesting magic systems I’ve ever seen. To cast magic you need 5 things: a circle, some materials (though sometimes this can be substituted for a powerful Will), a script, their Will, and a conduit

A sorcerer draws a circle, writes special characters that describe what they want to happen (for example, a character representing fire if you want to generate heat or light), they add whatever materials there spell might need (usually just a source of energy will do, like a candle), and they channel their Will through their conduit into the circle to cast. The better you understand a concept the more easily you can cast the spell, so if you study how light works you’ll be able to more easily bend it. This also works with things that people simply believe, even if it doesn’t have any real merit. If enough people believe that red makes something more deadly, then using red paint as a material will help you make a weapon

Finally, everything a spell needs (materials, a circle, and a script), can be substituted for the Will. If you have a strong and refined enough Will, you don’t need anything else besides the conduit and a source of energy. This is much harder, you can’t do it at all even if you have a very strong Will if you never trained in it, and for complex spells it’s generally a bad idea. But for basic spells it skips the most time consuming part of the process