First biggest productivity gain for Joe will be in using forward and reverse search for navigation (C-s and C-r in default key bindings).
C-s or C-r, type a few chars, <Enter>, continue editing
is an amazingly powerful way to jump around even a simple text file. No arrow keys, no mouse. I dare Joe to use this feature for a few days and try to go back to Notepad. (You'll be using it even to jump to a different point in the same line.) Also Emacs can be as minimal as you want it to be.