Cash is the primary currency in the game. It can be collected by spinners, or passively with a gem upgrade.
Gems is the secondary currency. It can be collected with the Gem Generator, or the bomb bouncer. As an alternative, it can be earned through ads, or purchasing in the store.
Spinners generate cash, which can be collected by bringing it within range of the collector, by bouncers, or by hitting corner bonuses. As a spinner fills up with cash, it turns green.
The collector is your primary way of gaining cash. You move the collector by moving your finger on the screen. You can throw it, or bounce it off walls. When the circle around the spinner gets in range of a spinner, the cash is collected.