The key to moving up is usually more attention to details, namely micromanagement. Minimize waste of shields, food, and commerce and you will see a more efficient empire. It's amazing how all the little things add up. In regards to your specific situation, Admiral Kutzov, I would recommend building a bunch of Mounted Warriors and taking several of the Korean cities near yours. Since they are colonizing a new landmass, they will probably not have a great road network, so you can probably catch many of their cities with spearmen and not pikemen, and Mounted Warriors cut through spearmen like a hot knife through butter. After you have taken 3-5 cities, they will probably be willing to give up tech for peace. If not, take a few more until they will give you tech. On another note, imagine my chagrin when I actually broke a knife trying to cut butter. I mean, I know it's supposed to be a "hot" knife, but still....