Making giveaways in my group

Hello guys, Im an admin of Mexican Fortress 2, we just start like 2 weeks ago, we are trying to get a tf2 dedicated server and that stuff, since there just a few spanish groups that actually work, so I decide to make giveaways on my group, but theres a lot of people that doesn't have enought games/money on their accounts to enter on this site, so im trying to find an alternative way and fair to select a winner.
Don't get me wrong Im not looking another SGift like website, just an alternative or a web app, I would appreciate if you guys could suggest me a few of them.
Also my group is not only for Mexicans, but its a Spanish comunity, feel free to join.

Meanwhile in Mexico~