The main shell in Linux is bash so presumably you mainly want to learn bash shell scripting.
At its simplest scripting is just taking the lines you run at a command line and putting them into a file then adding the execute bit to the file with chmod. Of course for more complicated scripting you need more but just being able to do that will save you a lot of time.
Anyway doing a google for:
Linux bash "scripting tutorial"
I got several hits the first of which was:
Going through a few of its sections it seems it may be a good tutorial. (Don't let the title of "Advanced" throw you off. It starts with Basics.)