Well the light should be taken care of first. You should probably get 6 or so 40watt (or higher) CFL lights.
Get some pots.
Some nutrient free soil.
Unless the walls are white, you should get some mylar to line the walls for reflectivity.
A timer for the lights.
A fan.
Some nutrients.
That should be enough to get started. If you end up needing other things later (like PH tester), you can always go and get it.