From the “Prerequisites” section of LFS:

Building an LFS system is not a simple task. It requires a certain level of existing knowledge of Unix system administration in order to resolve problems and correctly execute the commands listed. In particular, as an absolute minimum, you should already know how to use the command line (shell) to copy or move files and directories, list directory and file contents, and change the current directory. It is also expected that you know how to use and install Linux software.

Just start using it. Set up a dual boot if you really need access to Windows still, but try not to use it as much as possible. You learn by running into problems or holes in your knowledge, and solving those issues will fill in other gaps.

There are plenty of video series if you want to listen to advice before diving in, but there’s no teacher like experience.

Yeah SteamOS is nothing special. Any of the big distros can give you a similarly solid gaming experience these days.

Are you aware of recent events? Leadership has shown themselves to be fascist apologists.