commuting ain't so complicated for me because i keep things simple.

i don't wear cycle specific clothing; general purpose athletic shorts and t-shirts suit me just fine. i do wear cycling shoes with SPD cleats because i find clipless pedals to be marvelous, but they are by no means necessary. i also find that a good pair of cycling gloves to be benefitial as well, but again not necessary. and i do always wear a helmut when i'm on a bike, commuting or otherwise.

i commute with a backpack for my change of clothes when i get to work and other small miscellaneous items like phone, wallet, and keys.

as for gear on the bike:

lights
multi-tool
spare tube
tire levers
CO2 pump

that's it. in 3 years of bike commuting (30 miles/day), i've never needed anything more than the items above.