What are to-dos for beginner level system admin?

[hidezumi]

I have just started to try Google Cloud Platform to host small WordPress projects and unfortunately, I don't have a technical background.

I have a few questions. 

What are the minimum to-dos for a beginner-level system administrator?

I have tried taking snapshots (backup) and a VM manager to patch the Operating system. Are there any other things to do to maintain the system safely as possible?

Where do snapshots are stored?

I have checked the disk usage using the df command and found out 42% of 10 GB disk space. After taking the snapshot, I found the using disk space hasn't been changed though the size of the snapshot is 1GB. Is there any other storage generated? I mean do I have to pay for the extra cost every time I generate the snapshot?

I am quite new and I am not sure if I have chosen the right category for my question but I hope I can get useful insights here.