If you live someplace other than North America, you might not be able to easily get appropriately sized coins to use to make PennyGems. I recommend you look into the alternatives first, but if none of those coins are available either, you can buy twelve rolls of pennies (600 coins), enough coins for up to fourteen full-sized sheets of PennyGem labels.
Technically, six hundred coins would make fifteen sheets' worth of PennyGems. However, it is difficult or impossible to get exclusively brand-new coins. The rolls I get are a mixture of old and new coins, and some of the old coins are a bit corroded or just kind of nasty. Generally, there's only two or three coins per roll that are bad enough to be a problem, so 600 coins should be good for making about 550 tokens.
Why six hundred? Why not fewer, or more? This item will be shipped separate from the rest of your order, in a United States Post Office Priority Mail Small Flat-Rate Box. Pennies are heavy; that's one of the things that make PennyGems so satisfying to hold, which means the shipping charge for this is fairly significant, especially overseas. Six hundred pennies is the most I can put in the box without exceeding the weight limit, and because this particular shipping option is flat-rate, it doesn't get cheaper if I send fewer rolls until I get down to just two or three, and then I'd need to get my hands on some kind of special small box just for mailing two rolls of pennies. Meh.