Here is my current empire as the Mongols on H/H (I will try VH later):
As you can see, I have annexed the northwestern territories early on through an aggressive campaign of expansion down toward India, and I currently have the Chinese on the run.
The Chinese actually attacked me first, and though they fielded formidable armies early on with a lot of heavy infantry that crushed my weaker spear militias, I was able to wear them down by fighting them on the open fields where I could make use of my horse archers. I was also able to overwhelm their cavalry by ensuring that I set up military buildings as soon as I conquered each territory and building as many spear militiamen as possible. It also helped that they have the same religion I do, which made taking their northern cities easier.
As time went on I was able to isolate and lay siege to the castle in the Tibet region where the Chinese could not reinforce it, and though it had a strong garrison at first, they succumbed to a 10-turn siege without a fight. After this the Chinese were quite weakened, so I have brought three more armies down and I am currently pushing aggressively into their territory.
My first two attempts at taking Beijing through blitzkreig tactics were unsuccessful, but I will soon be in a position to deal the final blow! Ryukyu and the other smaller factions to the East shall face my wrath soon after...
To the West, the Turks and Novgorod are growing in strength, and I am concerned that my territories there may soon fall under attack, so I must act quickly to bring about my dominion of mainland China. The Indians currently fight amongst themselves to the southwest, but sooner or later one of them will prevail and then they will turn to my lands as well --and they probably won't want to have afternoon tea.
Japan is currently my ally due to mutual hatred of the Chinese aggressors, but once mainland Asia is mine I may betray them just to avoid loose ends. From there on I shall press westward to wreak havoc in Europe!