An ultimate guide could be a few tomes long not because you need to know that much, but because there are so many options and solutions. I’d recommend learning basics: core utils (i.e. command line tools), docker, network security basics (vpn, firewall).

Then as you start adding more services, you can identify gaps in your knowledge and close them (e.g. what is a database, how to manage it, how to back it up and then restore if it fails).