Well, the way most people go is to buy a retro kit, which includes a reflector, ballast pack, and the necessary cabling.
Others buy a loose reflector, an assembled ballast pack, and run/splice the wires themselves.
Still others buy everything as loose component parts and build everything by hand.
With the third option, you could probably accomplish this project in budget, including the lamp.
A basic spider reflector, which is of moderate efficiency, will cost about $35. It includes the socket. A magnetic ballast will cost about $50, or you can get an inexpensive electronic ballast for $90. A lamp will be about 60-80. If you add maybe $30 for some kind of box and some various bits of wire and hardware, you're at $235 per fixture for the most expensive of all options.
Later, you can upgrade your reflector if you want, but a spider will get you going. Frankly, the basic spider reflectors is what I use anyway.
Basically, here is your shopping list:
1. Lamp
2. Reflector
3. A 25 foot extension cord (you'll cut this up to make your power cord and wiring)
4. A "pull box" (you can get these from Lowes or Home Depot)
5. A ballast
6. A couple cable clamps, some wire nuts, and maybe a few zip ties.
A bit of metal drilling to get the ballast mounted in the box, and a bit of basic wiring will get you an operational system. If interested, we can certainly walk you through it.