Gold

Gold is one of the Resources you'll need to advance further. By getting enough Gold, you can build/upgrade Buildings, buy equipments from the Shop, fix your equipments etc. You can get gold pieces from your buildings - after a specific time -, by doing battles, gathering gold resources from the map or by visiting a friends.

Visiting your friends' Castle will give you +200 Gold (level doesn't matter), Farm can provide +50. Hence you own level Castle can give you +100 Gold, this is is rather funny...