Lights are a must for dusk and evening riding.
You don't need a light that illuminates the road perfectly, just that get you seen well.
I use a Cygolite Rover NiMH extra - It is very much bright enought to be seen (and to illuminate the road actually for 22mph speeds), but not excessively costly like the Night Rover brand which are powerful enough for full dark riding on single track trails. It cost me $74 on sale at REI, but runs $94 normally.
A good rear light (or several, one on seatpost, one on head or upper body) is important (see recent thread about a bright one)
Make sure you have pedal reflectors - they move and cars see that as a cyclist.
Wear a high visibilty yellow shirt or jacket - that helps for the dusk/dawn and catch headlights better.
Al