Basic SQL knowledge for sys/network admin is shrink db, mount/dismount. All of the rest goes to DBA.
Mix'n'match doesn't work good. You either stay out of the job because you don't know anything to the top or you work somewhere where they have the most basic stuff and don't advance professionally.
If you can get into big company as junior sys-admin, you'll have cisco/juniper, otherwise you'll need to get into Fortigate or w/e is "mainstream" for your region.
For backups I'd start with backup exec, starting with 12.5 version.
All of that depends on your target field. I work with SMB's, this means I focus on server roles, excesive knowledge with exchange, fortigate, symantec, vmware. Troubleshooting network = sniffers, monitors. Google-fu and jiu-googlitsu must be at the highest levels.
Learning that you are working 24/7/365.
On the other side, there are weeks when I sit and rewatch series/movies or just play games at work because everything works and microsoft auto update is disabled everywhere and on everything