Although I've been using variations of Unix since Version 5 running on a PDP-11/45, I use an Ubuntu desktop system for everyday use. Simple because it is easy to keep up to date and works well both as a graphical environment and with the terminal. My setup includes 2 LCDs in landscape mode for graphical apps and a third LCD in portrait mode exclusively as a terminal with lots of open tabs.
As for getting started, have a look at https://www.lifewire.com/beginners-guide-to-linux-4090233. Then you just need to frequently refer to the man pages and the many other guides you will find with Google. https://unix.stackexchange.com/ provides reasonably high quality answers to many common and not so common questions.
I recommend that you learn to use terminal commands well. As a pro tip, if you are using 'vi', CTRL-] is the same as ESC. When you get used to using that your speed will increase significantly. Oh, and remap the CAPS-LOCK key to be a CTRL key. You don't want to get RSI in your left pinkie.