I am an SRE and I have no idea what you are talking about. Clouds doesn't need to be "mastered", they just werk if you know what you are doing. So I would recommend to study more generic topics like servers, virtualization, networking, protocols, DBs, etc. Clouds are just a kind of wrapper for all of that.
Certificates are useless, they only make you remember theoretical bullshit which you'll never use. Learn through real practice.