Economics:
Money and revenue
Just like the game itself, WoE will use electrum as currency.
What can I do with electrum in WoE?
You can buy new cards. Each card costs the same (not different prices like Elements has). Rare cards cannot be bought.
You can upgrade cards. This can be only done in major cities and other "special places".
You can use electrum for fast travel between different parts of the map.
The richest players can even buy their own land (hexagon) and build a castle on it. They can choose the look, name, and appoint an army to protect it.
Those were just examples. There will be other ways to use money as well.
How to obtain electrum in WoE?
Each hexagon produces 1-3 electrum per turn (depending on the value on that hexagon) to the element that controls that hexagon. All that money will be divided by all the players in that element. This means that if an element controls 10 hexagons with a combined revenue of 20 electrum, and if that element has 10 players, each player will receive 2 electrum that turn.
You can obtain money by fighting and defeating enemies. When you win a battle, you salvage 10% of the electrum that player had in his/her possession (rounded up).
Some quests will give you electrum as a reward.
etc.
Post more idea here please.