I'm not professionally trained to admin a server. I'm entirely self-taught through tinkering, searching the internet, and pestering innocent developers on IRC channels. I just like the idea of self-hosting, it gives me freedom and the opportunity to tinker and learn about computers and the web, it's frustrating, intriguing and fun.
I'm a language teacher and I host some web apps for personal use and also to organise teaching materials for me and my colleagues, and I've learned a lot messing around with different web apps on a shared host (not so much on web server level beneath), but again, I have no professional training!
Web apps I've set up so far:
Friendica, Wallabag, Owncloud, Tikiwiki, Roundcube.
My first steps were made building my Owncloud instance from scratch, starting with installing Ubuntu server on my Mini-PC at home, setting up Apache, getting Owncloud to work and later switching to a managed server whose admins I can rely on knowing what they're doing :-)