If you're brand new to the concept, I'd go with something easy like Mint/Ubuntu.
To be honest, I disagree with that.My first distro was (and still is) Slackware, being not what most people call
"user-friendly". But the jump into cold water is the best way there is, IMO. Everything else, like Ubuntu etc. is a
mere waste of time since it's bloated and hiding a lot of the details. That's the reason why I linked vezzy's guide
in my previous answer. Still, it's probably possible to start learning with something like Mint / Ubuntu / whatever
popped up from systemd's lair, but in the long run, it's a loss. Feel free to disagree ^^.