Depending on what you’re after, the common recommendation to start with book of shaders or shadertoy may be counterproductive. In my experience using shaders, fragment shaders are a place where I spend a lot of time and effort, and I do a decent amount of computation directly on textures, but the sort of stuff done in fullscreen quad ‘picture in a box’ shaders as in Book of Shaders and ShaderToy is, I believe, unproductively mind-shattering and abstract for beginners. To learn shader fundamentals I’d suggest you write a particle system (in compute or in vertex+frag) or even a raymarching renderer or something, rather than just bang your head against animating patterns on a single frag.
