Well it sounds like you're serious about it. I'd always recommend focusing on where your passion lies. If that's embedded then c and rust are solid choices.

Just always be aware of what motivates you. Adjust your plan as you go. Find the balance between boring and frustrating. Did you know that the guy behind Google earth is a gardener now? That's totally fine.

I'm just saying don't torture yourself with your own fantasies, but always remain skeptical and cut cut cut. Choose consciously and then commit your full energy.

The only failure is to go against your own nature. Managing your motivation is way more important than optimizing performance. You can always refractor anyway.

That being said if you want to be thorough I'd recommend you start at c with a side of assembly. Stick to that until you feel comfortable and then move on into rust.

When switching you'll probably want to start from scratch because you've improved your design so much. You can always port it too or link it as a library. Don't worry about that right now, that's a future you problem.