Nice site- what steps have you gone to help people trust you?
I send physical items certified mail in the US -- both confirmation of delivery and returned signed green postcard. This protects both parties. I believe this shows the buyers that the seller doesn't want to get screwed either.
For first time buyers, I send each gift card separately so I do not inadvertently forget to include one in the envelope or an untrustworthy buyer claims they didn't get all the cards. Moreover, certified mail helps protect both buyer and seller from the post office! Case in point: I sent two certified items to a buyer and he only got one. He is an example of a highly trusted and honest buyer because he released the bitcoins from escrow before receiving the 2nd card. Anyway, I had to file a case to the USPS and the item was delivered next day after being overdue for three. The next time I went to the same post office to deliver a gift card, a worker I've never seen before was exercising a deep tissue massage with my letter in a nervous manner. I packed it much better this time to help disguise there was a card inside. He asked me if it was only documents. I said yes but was perplexed. Usually they ask the standard question if there are any hazardous materials, fragile items, etc. After pasting the green postcard on the letter, he goes into a second round of massaging the entire letter again!
There are stories on the internet with postal workers stealing gift cards from envelopes. In general, postal workers can be trusted 100%. It's the few bad apples that spoil the bunch. These bad apples are looking for holiday and birthday cards as well because they often contain gift cards. And when I bought a Walmart gift card, a cashier warned me never to send them by mail. She had hers stolen.