There are too many potential options to mention them all, but there are a few common ones which are frequently used to improve comfort, convenience, and safety! On the comfort side, one of the most important pieces to upgrade is your saddle. The saddles which come as default on bikes are rarely great. Getting a better saddle and one designed with specifically male or female anatomy in mind, can make a world of difference in comfort! Of course double check the height and orientation of your current saddle first, especially if you are experiencing pain and discomfort riding – it often means your saddle is too high, or too low, or tipped!
For convenience, many of us are hooked on phone navigation, so getting a handlebar phone mount will help you get to unfamiliar places in the city. There is a lot of construction across Madison in the summer, and bits of debris on the road can lead to flats. Getting puncture resistant tires can reduce your likelihood of flats substantially!
Finally there are two safety accessories which bike commuters commonly acquire. One is a mirror, mounted either on your handlebar or helmet, to keep an eye on traffic coming up behind you. The other is a bell mounted on your handlebars, to notify pedestrians on a path ahead of you to be aware that you are approaching.