how do you get the right to invite some1 else in this game?

cause if your get pick by the timer,you can't invite any1 so whats the other way to get your beta key except with that timer? i know you must have been invite but doesnt invite sented by beta members???

I'm pretty sure anyone who gets a beta key can get multiple beta keys over time. Also, GGG are setting up donation packages that included other stuff along with a beta key that they will be announcing later this week (hopefully).
The cheapest package will be $10 and this will allow you to get a beta key.