There are some discussions going on about career growth opportunities in CM. In my daily work I need to teach CM to students who would like to become professionals. What I see is that they really don't understand what they are doing and there is too much to know to glue it all together at start. This would be my recommendations how to grow in CM.
I would split CM stuffing by two - CM engineers and CM managers. Only just a few can do both. This should bring some clearance where to start. So junior can start with one of professions and when feel strong enough, can try to work on second. Any certifications will extend knowledge in one or other profession.
Engineers: build scripts, systems' configuration, automation
Requires high programming and analytical skills
Managers: release management, version management, codeline management, CMDB,
Requires high communication and presentation skills. Scrutability and keeping hand on e pulse.
When you can do both, then you are CM expert. Good luck!