If you decide to play full games, there are 60 questions total. If you buzz in first, which is not hard to do, you will get credit for 57 buzzes. One double jeopardy in the first round and two in the second round - no credit for buzzing in on those.
If you successfully buzz in first each time, you will get this during your 18th full game. Each game takes between 20-25 minutes.
The achievement will pop at the completion of the 18th game.