To spin the wheel, one diamond is required. The number of diamonds displayed on the screen (three, initially) indicates the remaining spins for the day. After exhausting these three attempts, players can watch ads to get two more chances, but a diamond is still required. The ads are meant to provide extra spins to players, but they do not waive the diamond fee to spin.
I noticed that a diamond was deducted for a spin from my account even though I watched an ad.
Last Updated: 89d