Another option would've been to sell it to a reseller such as Cardpool. https://www.giftcardwiki.com/ will show you the best rates per brand.
I do this for profit and made $5035 last year.
Can you elaborate?
Let's say you've been given a gift card to Lowe's you don't want. https://www.giftcardwiki.com/gift-cards/Lowe's
tells us that the best sell rate is either 82.5% from Cardpool or 87% from the GCW Trading club. The trading club is a private group. If you're starting out I probably wouldn't start there.
So you can create an account at Cardpool and mail the card in (many cards do have to be mailed in. Some do not. It depends on the reseller you're selling to. Some resellers accept electronic cards at lower rates.) You'll receive payment after some delay. I forget what payment options Cardpool has, but in general all resellers offer checks as payment. Some resellers will pay via Paypal and/or ACH as well.
As for how to make $5035 in a year, obviously you need to find gift cards to buy at lower than what you can sell them for. Deals can be found from http://deals.ebay.com/other-deals/gift-cards
(don't buy the pre-owned ones - you can't sell those), Costco, Sam's Club, Staples, etc.
To give you an idea of the margins, I pulled in $43k in revenues and had $38k in costs to get that $5k in profit from gift card reselling.