If you'll want to make your own cables, you need three main things:
1. The cable (you can buy a 500ft spool of it at Home Depot - more than enough to last you a few years)
2. RJ45 connector - these are the plugs - only 3 cents each (75 cents a piece if you go to radio shack)
3. A crimp/punch-down tool - this allows you to actually attach the RJ45 plugs to the wire. It works by pushing down the copper contacts on the RJ45 plug till they dig into the wires and lock in place. A very basic one costs around 10, 15 bucks.
Optional, but highly recommended: A cable tester. CAT5 is a pain in the $@#$@#$@# to make by hand. It's difficult the first time, and you're going to make mistakes whether you want to believe it or not. It'll save you lots of troubleshooting time if you buy yourself a cable tester. Expensive ones that test for signal-noise ratio, max frequency, data loss, etc. cost $2000 and up. Luckily, you could care less about these things unless your setting up a very large corporate network. The most basic cable testers
cost around $25, and they're more than good enough for testing if a wire is good or bad. Again, I'd highly recommend one (or atleast borrowing one from your school/friend) because you ARE going to make mistakes your first few times.