All the gameplay in Pirate Kings revolves around roulette. Players start with a limited number of spins and can earn more by waiting a while, winning them on the roulette wheel, or of course paying real money.
The roulette spins are your main source of income, giving you money both directly and indirectly. That is, you can win a fixed number of gold coins or the opportunity to attack another pirate and steal his gold coins in the process.
Attacking other pirates is very simple: you just have to choose what of his you want (his island, his ship, his decorations) and click to fire the cannon. In this way, you can get a hold of some of his money. That said, you'll have to be careful because other players can do the same to you.
Pirate Kings is a very simple game, and while it has very limited gameplay, it's entertaining enough to make you want to spend a few minutes a day spinning the roulette wheel. The graphics are pretty good, too.
Requires Android 2.3 or higher