Nim, D, or possibly Python with Cython/Pythran/Nuitka/etc. acceleration (maaaaybe Go). These all have shallow learning curves and easy FFIs to C. That allows

Nim, D, or possibly Python with Cython/Pythran/Nuitka/etc. acceleration (maaaaybe Go). These all have shallow learning curves and easy FFIs to C. That allows you can do easy things first and worry about hard things later/gradually. Of course, you really need to be more precise than "systems prog.lang" as I would say there isn't great agreement on what that means. Giving a set of task categories would be better. E.g., if you want to write kernel modules for OS? then you should learn whatever language OS? is written in.