Most Linux distros use BASH by default---this is a very common shell and your time will not be wasted.
I would start with "Bash Guide for Beginners"--free at http://tldp.org
In a terminal, type "info coreutils"**. This gets you a synopsis of some more common commands. Another good trick is "man -k <keyword>" For example, "man -k file" give you all the commands relating to files.
**You might have to install the "info" utility using your package manager (Adept or Synaptic)