Good choice, especially with regard to their POWERFUL military, but a difficult one also, especially because you'll get into contact with the horde soon (which gave me a real hell). Your initial neighbours won't bother you exceedingly, especially the Lithuanians have excellent generals but will ruin themselves in wars with Poland and the Novs. You should exploit these early conflicts to your advantage, so grab Novgorod if the opportunity shows up. Leave Estonia for now, it'll require quite a bit of garrison which can be used more effectively elsewhere.

Since your position is somewhat precarious in the face of the Horde (and you have no rivers or heavily forested battlegrounds), try to grab an emergency refuge from which you can rebuild your forces - Sweden ist the best possible choice, it's rich, it's quite safe and it has iron! Get rid of the Danes if they prove to be too annoying but stop expansion before getting into a war with the HRE or any other major power. It's not really rewarding at this stage, and the East should occupy your attention by now. One you've weathered the Horde (or whenever you feel strong enough) take Prussia and hold unto it. The +1v Teutonic knights you'll get from there IIRC are among the best cav units in the entire game.

A word to GA. Your goals are limited, and so will be your points count, so you may have to resort to the domination option (I did so in my TO GA game because France had built an unsurpassable lead in the count). GA means turtling at least for some time, but since your holdings likely won't be particularly large it also means that your king's influence will be somewhat low most of the time, making it difficult to get good heirs. They partly make up for their generally meagre quality by being excellent fighting machines (you'll probably honor those uber 40-men bodyguard units) but don't really make up for a good dynasty. Well, maybe you have a better way of dealing with that than I do....