Linux

Bash syntax - I recommend Unix Power Tools by O'Reilly, but it is more advanced so maybe start with a basic version. People look at me funny whenever I say this, but I started myself with something like Unix for Dummies. Why not!?

Keep in mind that this is no trivial task: bash is basically a programming language unto itself - it even has conditionals, loops, variables, etc. Yet SO worth it if you use Unix and want to know more what it is doing.

You also should have a basic familiarity with Unix foundationals as well, to know why something such as this is very dangerous:

export PATH="~/bin/:$PATH"

So, the easy way would be to just take the nice file, copy it wherever you want, and leave it at that. The hard way of actually understanding it may require a deeper dive into Unix. Unix Power Tools, with the picture of a drill on the cover, or maybe someone will recommend a better option but that's what comes to my mind.

Have fun!:-)

So you can do what you like, but if you are going down the road of shell customization, I recommend you first consider if bash is the shell you want to keep by googling around and reading some articles.

I personally use ZSH (and I cannibalized ohmyzsh for the few configs I wanted instead of taking the whole giant bastard of a thing) but fsh is a fine choice if you don't care about posix (a different discussion). There are some other options to consider as well, but if you're gonna configure, don't do it then do it again in a month with different syntax lol.