I don't think a lot of those things are worth learning. I would never consider using git from anything other than the shell or email from anything but my favorite client. It's all personal, of course.

> Perform autocomplete on my Python/Octave code

.. except for auto-completion, who doesn't like that? :-/

Try the 'dabbrev-expand' command for auto-complete in any mode (naive match on other words in the buffer): M-/

Then check out 'C-h a expand' and 'C-h a complete' (apropos searches for commands related to code completion).