The most important thing is to get a good light system. Now is a good time to buy one because lots of places should have them on sale with longer days and daylight savings. Magicshine may be a good inexpensive option if they ever get their battery problems resolved; until then I would steer clear. I've got a Magicshine that I can't use due to battery problems and replaced it over the winter with a Light & Motion Stella 300, which is nearly as bright but with a much better battery and run times.
The PB Superflash is a great inexpensive tail-light and there are other comparable ones made by other brands. I use two of them.
Bright clothes are also important. In summer, a jacket may be too warm but vests are a great option. Look for neon yellow/green, which is most visible. I have a whole collection of yellow/orange/red jerseys that I wear commuting when it's too warm for jackets.
Remember to slow down when riding in the dark. No matter how good your light system, it's easier to miss obstacles, potholes, sticks, rocks, etc. when riding in the dark. That's also a good reason to use larger tires than you might use on a regular road bike. My commuters have 25-28 mm tires.