Clash of Clans top up across 80 Gems, 500 Gems, 1200 Gems, 2500 Gems and 6500 Gems. Every seller is identity-checked, and every payment is held in escrow until you confirm the order arrived.
You give your in-game ID at checkout and the seller tops it up. Instant listings deliver within minutes.
Yes. The seller is only paid after you confirm the top-up arrived.