What is the best path for learning low-level computing?

Hi everyone, I had made a topic about creating an OS from scratch a while back, and I realized that it would be much too complex of a task for a simple Python developer like me.

With that said, what is the best route/roadmap to eventually lead up to building something of that complexity, and what resources will I need to practice (expanded upon in the next section)? Are there any prereqs before jumping into some of the basics? All I really care about is getting close to the hardware, and possibly eventually creating my own with enough understanding.

I do have a bit of an understanding of logic gates (AND, XOR, etc) after watching some of this series called Exploring How Computers Work, but I can’t actually implement anything without watching a tutorial. I have a basic understanding of how computers function (RAM, CPU, etc). I have an Arduino, which I’ve completely forgotten to use, and would be willing to buy other mostly cheap microchips such as a Raspberry Pi if needed. I can download free software and anything else required.