On some Peer to Peer marketplaces, reselling giftcards on a same platform is considered as a violation of their Terms of Service. Because it can be abused by scammers, using one giftcard for different trades and scam different trade partners.
If you only want to purchase gift cards for your personal use, it's fine but you have to know risk of reselling giftcards like I said. At least the risk is big if you resell a same gift card on a same platform where you bought it.
When trading gift card with a trade partner, you must have a screen recorder that can be used as a proof of trade when you need to make a dispute.
Redeem gift card quickly because if you are late, the trade partner can scam you.
How to Safely Trade Gift Cards on PaxfulAmazon Gift Card
Ask your buyer to upload the gift card with proof. This includes a photo of the receipt.
Take a close look at the receipt. See if the receipt is under your trade partner’s name and look at the date of purchase.
Ask if their account is restricted on Amazon. Ask them how often they sell Amazon Gift Cards—if they do it often, it’s likely that their account is restricted.