Having experience in ruling a kingdom is very important. Experience Points - or XP - can be gained by completing tasks and quests in the game. You can only earn this from winning battles.
By venturing forth into the single player campaign of the Dawn of Titans world, you’ll find many different story quests and tasks which will let you earn XP. gaining more of this will increase your level and leveling up will reward you some Gems and Portal Stones that you can use to progress in the game.