I have posted in the main thread yet, and I have mined it for 3 days, thanks a lot!
9JdPmQjjRyvXr2wyNmUitvRQ8WqdLyTn9h
PS: I want to buy some GRA with BTC, who can be trusted?
I'd suggest you to wait for it to be added to an exchange. Otherwise you can always post a message at the main thread, maybe someone is willing to sell. But be very careful about trading without an exchange.