Coins aren't currently implemented ingame, but they will be in the future. However JCoins can be purchased from Jagex, but can only be spent on WoLCash and to repay owed debts.
Jagex Coins or JCoins are a form of currency in 8Realms which can give you "the ability to queue buildings, research or orders so that if you're going to be away from the game a while, you know your Empire has plans in place". As stated by Jagex on the 8Realms News List , the coins will not allow you to buy resourses, buildings, advance through ages or any other way that makes you faster in the game.
Purchasing JCoins