Novgorod starts out with a decent ruler, who's father is the ruler of Kiev, and at various times will cover what is now St.Petersburg. Connected to the Baltic sea, you will have allies as your dynasty rules all across what was Medieval Russia, but they are divided into may different kingdoms, civil war is guaranteed. You are located next to the Baltic pagans, Finnish pagans, and catholic Scandinavians; Holy wars creates opportunities for land gain in which you will require if you ever happened to become a strong kingdom.
However, finding claims is quite difficult for the most part. It would be recommended that if you ever happen to find a Rostovian girl with claims, marry her, and them press those claims before Rostov takes the throne before you do.
Side-note, stalling for too long in this time frame, if Rostov should ever happen to acquire the title of the Kingdom of Rus before you do (or your country is ill-prepared to fight their army), face yourself doomed and restart and try again. By doomed, I mean once that country gets the throne, he will instantly excommunicate your guy to the depths of hell and your country will eventually be taken apart bit by bit by both Rus and eventually their allies, i.e Norge.