Theres two types of lights that are generally used for vegetative growth. Flourescents and MH bulbs.
If you only want to grow one plant and dont have a whole lot of cash to be spending on the lights go with Compact Flourescents (CFLs). These are the energy saving bulbs you can buy at wal-mart that are spiral and only cost about $8 for three of them. These are 24w bulbs. If youve got a little more cash get the bigger ones. Three 24 watt bulbs are plenty for about the first 1 1/2 months of the plants life. Once it gets bigger you may want to get a few more. You can also buy light sockets and the cords to plug them into the wall at walmart. they are in the hardware section.
If you have plenty of cash, want to grow more than one plant, and want to grow primo bud, MH is the way to go. These are rather expensive because they have to be hooked into a ballist. The ballist is what costs a lot. I suggest buying the MH/HPS conversion setup. HPS is the light used when flowering. This way you dont have to buy a whole new light when you need to flower. They cost around $200. You can find them on eBAY.
The MH will grow the plants faster and stronger than the CFLs can. But the CFLs can do the job if you're just growing for yourself.