For this you need to have greek premium.
Easy ways to get xp:
1. Neighbourly defense quests - This quest can be accepted at another players city ambassador, these quests give you quite a bit of xp each time and only takes around 10 minutes (Repeatable every 12 hours).
2. Sarta PvP boosting - This method can be a bit more time consuming as the matchmaking system in this game sucks, it will make it alot easier if you find a boosting partner around your level. Once your both in the game wait four minutes (that bit is important) and then the losing player can quit and it will count as a win to the other player.
3. Trade Quests (Mosaic Tiles, Delphi,Giza Limestone) - These quests can sometimes be difficult to understand and play but you will get used to them, if done the first time they can both be done in less then 20 minutes with quite alot of xp (Repeatable every 12 hours for each one).
4. Lots of Rogues - Another Easy mission, this ones available in Argos (It seems to have disappeared for me, anyone know where it is?) It Starts of as a normal quest which is then repeated 4 or so times with increasing difficulty each time. After that it will become a repeatable and is done in around 5 minutes (Repeatable every 12 hours).
5. Breaking Omlets to make an Egg - Another argos mission but this one is a little more difficult, once you get to know the strategy though it is easily doable with good equipment on your fortressess and it only takes 30 minutes (Repeatable every 12 hours).
6. My personal favourite and the best way to earn xp on the game, though you will need the skirmish pack. To do this use MICKERR's guide to getting the sphinx achievement which can be found here Solution for Sphinxed! in Age of Empires Online (PC)
i wont give all the details because i dont want to steal the method he found but basically this way you get a huge sum of xp in a day and you idle most of it. This method can take an hour or two though but i feel it pays of the best and gives great gear.
If anyone else has any methods they want to add just comment and I will add it to the guide.
*Note: xp for nearly all if not all of these methods varies depending on your current level*