I would focus more on the frame than anything else.
When you first start commuting you have no idea what you really
want/need until a few miles /months later. If you're like most people,
your commuter bike will end up being very different from what it
was when you bought it as your skill and miles build.
In any event : Lights, mirror and rack to start. Go through a mock
flat tire fix so you know what to expect (you can patch tube without
removing wheel most of the time) and what to carry.
Good luck on your new endeavor !
