How to network a card game?

I just started learning about different ways of networking with Unity and i'm looking for the best way of approaching an online card game. Do i need to have a custom server scripted and if so where would i learn more about this? And does will the server have it's own database on a local computer or should it use a website hosting database with mysql? In the future I would hope to put this on IOS. Any tips on where to start would be greatly appreciated.