Good cycling gloves are essential if your going to be cycling any amount. Gel padding helps cut the vibration reaching your hands causing numbness.
Also some cycle shorts or tights (depending on weather). They might feel strange to wear initially, they sometimes feels like wearing an adult nappy (diaper if your in USA) but your backside will thank you very soon.
If your going to be on any unlit roads at night make sure your front light has a decent beam. Don't rely on a little light because a car heading the other way will kill your night vision instantly.