Unless you work odd hours, you won't need lights until Fall.

I would concentrate on storage and visibility first. That means a rack and panniers or a backpack, and a brightly colored top.

I used a backpack at first but got tired with my back being sweaty all the time. Panniers are much nicer, but expect to spend about $100 for the rack and some basic bags.

For the top, I went to Home Depot and got a construction vest for $10. It looks silly, but it does the job. The reflective strips are nice when it's foggy or generally gray.

After you ride for a bit, you'll get a better idea of what's needed and what's not.