You know why they're called gifts right? Charging for beta keys that you got for nothing, you big meanie.
And also very uninventive, you could have asked people to write a haiku about their elbows, a poem about Denmark or draw you a picture of a horse and the winners get the gift. I was seriously considering asking people to write a haiku about how awesome I am in exchange for my CS Global Offensive beta gift, but I went for the boring option and just gave it to someone, for free.
If you want to get in on the beta, but don't want to pay because you don't have to, go fill in the survey on the dota2 steam page. If you fill in a survey you get a chance of getting a beta key, just search Steam for dota2, then scroll down to "Join the game" and click "Dota 2 survey". If desperate maybe ask friends to do the survey and give you the beta gifts if they get in.