Early (hard)- as that's what I always play especially as Novgorod
Invade Lithuania on turn one with your king (to match the star). The problem with Lithuania is that it has only one province and "troop build-up" is faster than say Kiev that has two which mean they'll attack you sooner. After that you can either bribe or fight rebels except Prussia and Livonia/Estonia (whichever is more rebelious). After that I'd suggest taking on Volgas, Poland (too busy governing Prussia usually lol), Kiev, or Cumans (who are usually busy and weak enough to be left alone for a time being).
In my campaign...
I tried to "migrate" west as fast as possible because I didn't want to fight the initial Horde spawn but I was back stabbed by Volga-Bulgars so I had to eliminate them with the help of Kiev who was nice enough to me since the beginning. So I held most of lands north of Black Sea. Then I took out Sweden, Norway and Denmark who were the weakest. This was a mistake I think because later on Kiev attacked me. They were still weaker compared to me though - I had more and better troops. It's just that I put them on other end of my empire. They were gone as soon as I weakened English (another mistake) and garrisoned Northumbria and Mercia with enough troops to let Scotland remergency poured into Northumbria. Now I'm busy fighting Alhomads who had taken over Spain and pushed through Pyrenees as far as Wessex. French and English are down to one or two province. Then I crashed as I was fighting a big Almohad relief force in Flanders and haven't continued. To my surprise the Caliph has only one star. So I'll be glad to reload the battle lol.
It's not even 1200 yet but if the horde appears now I'll be wiped out just so you get an idea of what my kingdom (and what yours would) looks like. I interfered with Western affair too early. I think the key to Novgorod success is either you wipe out everybody before 1230 (which is unlikely) or consolidate a big enough empire but not without careful border planning to keep churning out units to send to Muscovy and Kiev. If you don't have enemies sending out ships to North Sea and the surrounding, British and Scandinavian provinces can be easily kept without big garrisons.