Where will you be parking the bike at work? How much is your bike worth? The reason I asked those questions is because if you bought the bike within the last year you paid around $900 for it. And if your parking it in an area that is subject to crime do you really want to trust a $900 bike to $150 locks? Any lock can be defeated and be defeated quickly. If the bike is over 5 years old the value of it isn't much and may not be an issue if it gets stolen. If getting it stolen is worry for you then if I were you I would buy a cheap used bike for $100 or so and lock it up at work with a medium duty lock and not worry about your better bike being gone when you get off work.
You could get a large handlebar bag and put all your stuff you need for work in there, and some bags have quick disconnect feature and come with a shoulder strap, thus the handlebar bag turns into a shoulder bag. You could get a messenger bag but those you have to ride with it slung over your shoulder, some are ok with that others are not.
Another poster gave you list of stuff to carry, adding to that I carry a ultralight folding tire I keep bound with a couple of those strong black rubber bands that inner tubes use. A tire like that can fit in a seat bag, or in a handlebar bag. A spare tire is great thing to have if you by some weird chance destroy a tire, and usually the tube too, you can slap on the spare stuff and get to work without to much delay. I also carry a Park Boot patch in case I get a cut in the tire I can reinforce it from under the tire to prevent a tire bulge, and then a small tube of SuperGlue to fill in the cut from the outside. Doing that will prevent any other road debris from entering into the same cut and blowing the tube.
If your going to be using lights of any kind you should carry spare batteries just in case a light goes dead while trying to get home. I carry one set of AA and AAA bats for my front flasher, bar end lights, helmet lights, and my main rear light, but I only carry one set of each because it's unlikely all those lights bats would die at the same time.
Carry personal ID and medical cards with you. And please wear a helmet.