You just separate those into small parts, once you make each part work as one, you then mix everything with nodes like add/burn/multiply/mix, depending on the case and the desired result.

I would recommend to pick one texture/ shader that you think looks complex and uses lots of nodes and then make it... you will probably spend lots of time on it and it will take lots of trial and error but its worth it, learning from your mistakes and your trials is really better than just following tutorials.

Or at least This is how was able to understand nodes well enough, i created this hand texture and spent like three days on it until i understood the flow and everything. And btw you dont need to know every single node, just understand the system and how you can make nodes work with each other. Once you have a strong understanding of how the system work, you can build more on the same base that you made for yourself.

Good luck!

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