ClixGrid is a game of chance. It's just random like rolling a dice. The odds of winning are about 1 in 400. You may win twice in the same day or none in several days, it's totally random.
It doesn't matter where you click in the grid, how long you have been a member, how long you have been playing, nothing really, it's just sheer luck.
The total amount of the prizes available depend on the purchased adverts.
Good luck