Step 1: Materials
PVC - I bought one thing of 10ft long, 2 inch wide PVC. You can buy 2 foot pieces would, theoretically, still sound just like a rainstick. I just wanted a GIANT rainstick, so I bought this one. You can also buy the pipe thicker, up to 4 inches, but I didn't want to have to buy the extra length screws and the price different was pretty large.
My 10ft piece of 2 inch wide PVC was about 6 dollars, but it gave me enough pipe to make 2 rainsticks.
End caps - You need to cover the end of the pipe in some way, I'll cover other options at that step in the process but the easiest way is to buy end caps (located next to the PVC pipe). They run about 1.50 a piece, and usually make everything a lot easier. You will need 2 per rainstick.
Screws - I used 1 5/8 inch drywall screws, just because that was what i had around. However wide your PVC pipe is, make the screws as close to that length as possible. This allows optimal bounce-a-bility for your rainstick. Also, you will need a lot of these, my rainstick used at least 30-40.
A new thing of screws costs about 5-6 dollars, if you have old ones, use them! Good chance to get rid of some rusty, otherwise useless screws.
Filler! This is the fun part. You need some sort of small bouncy particles to be the "rain" in your rainstick. I used uncooked popcorn kernels and rice, but I've heard of people using beans, pebbles, marbles...be creative! The larger it is, the slower it falls, mix it up and no two rainsticks will sound the same!
Cheapest filler would be a bag of popcorn kernels, about 2 bucks AT MOST.
You will need a way to drill holes, and a screw driver. I used a dremel tool, as that was all I had in my apartment. If you know another way to put screws into the pipe, do it, but I didn't have a power screw driver, and even if I did I was afraid it might crack the PVC.
This is expensive. Borrow one if you don't have one.
Hot Glue Gun- Due to improper planning, I needed a glue stick. You might want one too, just to securely fasten all the screws in place. I would also suggest borrowing one if you don't have one, but honestly you should buy one. Hot glue is amazing for crafting, and almost essential in most of the stuff I do. Buy one at some point in the near future.
Hemp/cloth to wrap the pipe in
Stickers/markers/whatever else you want to decorate it with
Total necessary cost, if you have to buy EVERYTHING (but can borrow the tools)
Approximately 20-25 bucks for two 5 foot rainsticks. If you find things cheaper, but them cheaper!