Plus, you have a maximum of only holding 500 Spins before you cannot hold anymore. This can be increased by purchasing the Shinobi Life 2 Spin Storage Gamepass. But you do not want to lose any Spins, ...
A Free Spin refills every 12 minutes, but you shouldn't spend them as soon as they fill up. Instead, try to save them as long as possible because you can then take advantage of the 2x and 3x ...