You can either get lucky and find 1 per night or you can use the slot machine. And also be lucky. A roll of 666 yields a gem. Anything else is 5-5000 tickets
niles restaurant may have one in the Ankh on the right, greeting center will have one by the circular platform in the middle, goo room can have one in one of the lockers, sammys stage would have one in the electrical panel when it breaks down. I check all those real quick at the start of every night for easy gems for easy toys. Then just grind out the slot