I would recommend Poland. It can be challenging until you learn to use your two main cavalry units. Don’t worry about seiging cities…just take three of four spies along and storm the gates. Your infantry is also good but your cavalry is so good you seldom need them. The woodsmen are cheaper than peasants on upkeep and can handle most any other infantry units if handled well. They also have a stake using archer unit when it is called for…

Who ever you choose, have a blast.