The lottery is one of the shops that can be built, but unlike the other shops, you don't make any purchases. Instead, you just get a chance, once a day, to win an item. This is not done via ID as previous lotteries but is actually completely randomised. As you rank up the Raffle Shop stores, your chances of getting the top prize are increased.
So,it the prizes only depend upon the no. of points you have in join avenue.
Bulbapedia might add a percentage soon in the future.But this is all I could find.If there is a %,i will edit this ASAP.