Good advice. I'd add that you should think out the logistics. What can you leave at work? What will you shuttle in/out on your drive day? What must be carried on you or on the bike daily? Plan for how you'll carry at least that much. Many people begin with a backpack, then switch to a rack-mounted bag or panniers.

Your budget will dictate how much of these things you'll start with and how fast you can purchase to adapt to your needs. \

+1 on the frame pump and patch kit. You may want to carry a spare tube, too, as it's faster to change. You can then patch at your leisure without delaying your commute in to work.