Isn't Arduino a sort of simple C++, not C? Also, for most beginners to embedded development I would recommend starting with ARM devices and a JTAG programmer for anything beyond simple blinky-type programs with Arduino. Being able to step through code and see the various hardware registers is helpful.

And as great as Rust is, it is hard to set up with embedded right now. Maybe someday, but for now I'd stick to C unless you really want to play around with Rust specifically!