Virtual Coins, in one direction only
Coins come in from the daily bonus, missions, tournaments, winning spins and the official links, and they go out on bets. That is the entire economy. There is no cash-out screen, no prize catalogue and no way to transfer a balance to another player, which also means nobody can buy your Coins from you. The game holds no gambling licence because none is required where nothing of monetary value is at stake.
The Golden Ball draw is not a cash prize
This is the part worth being explicit about, because a draw sounds like a raffle. Broadcasting wins earns Likes, and Likes improve your odds in the periodic Golden Ball draw, but what is drawn are in-game rewards. It is a virtual prize draw, not a sweepstake with real-world value, and no part of it converts to money.
Why it looks like a casino
Because it is built to. The machines are styled after Las Vegas cabinets, the reels resolve on random outcomes, and big wins are presented with the full celebration. That resemblance is the product. The difference is that a licensed casino ends the session with a balance you could withdraw, and this one ends it with a number that buys more spins.
What your money buys
Coin packages, and through them playing time. Public materials do not publish exact amounts per package and they change with promotions, so the store is the only place to see current values. As with any social casino, purchases are final and nothing accrues value. If you spend, set the amount before you open the store rather than after a losing run.
Is it legitimate?
Yes, as a game. It is developed by Jungle Soft, distributed through the App Store and Google Play with hundreds of thousands of downloads, and playable on iOS, Android and Windows through Google Play Games. It does what its listing describes. The risk worth knowing about is not the app but the sites around it promising codes, generators and cash-outs for a game that has none of those things.
The free way to play
Take the daily and timed bonuses, clear the missions, broadcast your wins for Likes and Golden Ball entries, enter the tournaments, and claim the Facebook links, which are worth 200,000 Coins or more each. That last one is what this page collects, newest first, so you can see everything still claimable at a glance.
Every free Coin source