There are any number of tutorials you can find on Google or duckduck go or any search engine. 😉 I have heard it said that building an Arch Linux instance "from scratch" using a tutorial is a good learning experience for a moderate skill user.

A few key skills jump out at me as a casual CLI user:

• Package managers (search, install, and uninstall packages, add repositories and refresh package lists)
• Compiling packages as-is from git repositories isn't all that hard with a tutorial
• Editing configuration files from command line using vim/emacs (don't use emacs lol) is a must if you're ever in a situation where the DE won't load
• Grub menu: if you have a problem booting, editing the file your computer uses to set boot flags is a very valuable skill
• Watch some YouTube videos about Linux distros to see their philosophy/usages. For example: Debian is ultra stable with long release window and WIDE hardware support so stuff gets out of date but it runs on a potato, Arch/Manjaro/etc is rolling release with less stability but fastest updates, Fedora made by Red Hat is useful for enterprise, Linux Mint/Ubuntu are very user friendly, Puppy Linux is user friendly and very lightweight, Gentoo is for if you want to compile all the packages yourself (A HUGE PAIN), etc.
• learn what a desktop environment is and how a display server (xorg or wayland) works
• The man (manual) command is your friend! The syntax is "man [any command/program here no brackets]"