It can boost testosterone.
It's pretty cheap to make one, depending where you live though. I bought zinc rods from Finnish supplier, although I bough my first ring from a vendor. (I'm not linking any companies!)
Anyway, silicone tubing is nice, you can replace it from time to time. Of course you can opt to buy the black rubber kind which is usual when you buy from a vendor.
Getting copper is relatively easy, your local hardware store should carry suitable copper pipe. (It doesn't have to be solid copper! Just food grade, as in what you might but into your water system.)
Getting zinc rods can be a bit more difficult, you may have to order online.
All in all, one ring should cost you around 5 euros / 6-7 USD. (I can't remember the exchange rate at the moment.)
I definately suggest making one by yourself, as you don't need fancy tools. A decent metal saw, scissors and maybe a metal rasp / file is all you need.
In my terms pretty simple.
Purchasing the material will probably be the biggest task in making ROP.
But anyway; Do it!