I think there are two major parts in learning how to use material nodes.
- I think you definitely need to know what nodes exist and what they do. So you can watch some tutorials or just go through the nodes, and make sure to learn what each does:
I mean you should be familiar with the whole menu and sub-menus and at least know that they exist and have a at least a rough idea what each one does. Documentation might even be useful here.
- The other half is learning how to use them. That one is wider and more difficult to learn. You can watch/read tutorials, attempt creating solutions for what you want to atchieve and practice in general to learn various techniques and ways they can be used. This is more like learning a skill, not only information, so it takes practice and time.
One important bit that you now seem to be missing is that math and other nodes are not only for working with color. Manipulating texture coordinates is also a very important part in making procedural textures. You can think of coordinates as if they were color as well, you can even view them as these gradients:
And when you do math operations with them you can manipulate the placement of whatever texture they plug into:
That’s a big concept in procedural textures.
Anyway. Learn the information(what the nodes are), then the skill part - the techniques how to use them(this includes practice).
I think video tutorials are helpful, but written info(with pictures) is also valuable. I think there is a lot of great information about techniques here on these forums as well as Blender Stack Exchange. You could look for examples what can be done.
So I am afraid there is no way to learn without practice. It is essential, because you are learning not only the information about what each thing does, but also how to combine them in truly infinite ways to atchieve some results. So it’s a skill that you are learning, not theory and therefore it’s impossible without practice. I think you need to accept that, but at the same time, you can aim to do this learning in a more organized and efficient way. If you know that you need to learn techniques, that’s what you should be looking for and concentrating on learning. Hopefully that might make things a bit easier.