Hello!

Events like Lucky Stars Wheel that has a Jackpot Ninja as the Main Reward is purely influenced by RNG. There is no exact or accurate count for spinning to get it but a chance only while doing it. I'd say, never spend on these kinds of events if you will only target the Jackpot Prize but rather save up and buy it somewhere that you can definitely obtain it. Some might get it for as low as 20 coupons but others might end up spending tons of coupons and still not get it. Thank you.