I dont think anyone that replied really understood what I was asking. So.... I understand how to sell and buy giftcards, but what i do not understand is how I get my btc replenished after doing so
No one here knows, or is going to tell you how exactly they do it.
I could make an educated guess though;
1. they sell you BTC for your giftcards.
2. they then resell the giftcards, or services that the giftcard provide to a third party with profit.
3. Use profit/returns to buy giftcards again.
...
4. Profit.
Now how
exactly vendors create these traderoutes, is something they're probably not going to tell you, otherwise they'll soon be out of business/get less profit. It's really up to you to find something that works.