Quality hormone- I recommend dip-n-grow as by FAR the best bang for your buck.
Medium- You want something that is either sterile, or inoculated with beneficial bacteria. Rockwool cubes and expanding peat pucks are popular, and Rapid Rooters are WONDERFUL.
Tools- A pair of sharp scissors, like the ones you find in the makeup section for manicures. An X-Acto knife with fresh blade, or razor blades. If you plan to clone frequently, go for the actual knife. It's safer to work with.
Light- One clip-on desk lamp with the SMALLEST CFL you can find.
Spray bottle- This should be clean and able to deliver a fine mist
Humidity dome- Either a commercial propagation tray with an 'altitude' style dome (the tall ones), or a clear plastic storage bin with a lid. The lid will be your tray, and the bin, your dome.
Anti-transpirant- This is optional but VERY helpful. Wilt-Pruf or Anti-Wilt are found at florist shops if you don't have a grow shop or farmers supply. Wilt-Pruf is MUCH MUCH cheaper if you buy it as bulk concentrate.
Heat- Only if you cannot maintain a constant 70-78'F in your cloning area. Usually the top of the fridge is plenty warm, but if you live in a 2 bedroom, 1.5 bath igloo in a nice subdivision (yes, I know there are some Canadians here heh heh kidding guys), you might want a 'seedling heat mat' under the dome.

All your gear will cost under $50, but the heat mats are another $25.