I think a good exercise is to build a CPU/Micro simulator in a more modern language. Followed by writing a compiler (for an uncomplicated language) to target t

I think a good exercise is to build a CPU/Micro simulator in a more modern language. Followed by writing a compiler (for an uncomplicated language) to target that CPU. Should teach you most of what you need to know. I remain reasonably agnostic to what language people should learn first, whether it be C / Java / C# / Python / <some other language>.