I also disagree with Muscovy for a new player. Too many things can ruin it for a new player:
1) handling of Poland and Lithuania
2) handling of Denmark and Sweden
3) opportunist hordes might jump on a new player, including if fighting Novgorod
4) separatism issues conquering neighboring horde land will bring for a new player.
I'm not saying Muscovy is hard, especially once you know the tricks of the game, but a new player is not gonna know the tricks of the game. There's quite a bit to juggle on Muscovy's borders imo. Sure, Muscovy is a cakewalk for an experienced player but that's not what we're talking about.
To me, a new player would want someone that has lower risk (fewer neighbors, and those neighbors are less likely to go after ya). Muscovy has great potential to expand, but they aren't exactly in an area of low risk for a new player.