In terms of the bike if you commute every day its going to get dirty. I've picked up a couple of mean second hand middle of the road bikes over the years and got good mileage out of them. Current one has done about 6000 kms and still going strong. I paid $AUS300.00 for it so have got good value for money.
Avoid steel rimmed wheels if it rains where you ride.
For me when I'm commuting the golden rule is "light is right".