Russia is one of the factions I tend not to expand with. I mean, the Russian economy is delicate and needs improvement. So, if you conquer the whole lot of territory from Novgorod to Moscow and beyond, and further southward, you have to spend more money on each city for maintenance, improvements and military means. If the Russian acquire too much territory they get trapped, their troop numbers are spread thin between cities and some cities are neglected by the user for being too far off and unimportant. I tend to play the best with Russia when I stay in a cozy, minuscule empire, yet an empire that is economically sound, technologically advanced, and militarily-strong so I can eventually launch an attack on Poland. I would suggest using your Orthodox brothers, the Romans, to good use as well, such as setting up conflict with the Hungarians, of whom would most likely support Poland or be unstable allies at best for Russia.

As for units, one thing I noted about Russia is that their early on units contain militia, mostly, but there are some exceptions. The Kazaks are pretty good troops. They are horse archers with wicked speed, perfect for hit and run raids. They carry a small sword, so should be kept out of hand-to-hand combat but in terms of archery, they are simply wonderful.

The Boyar Sons are also worth noting. They can double as missile troops (when wielding the javelin) and hand-to-hand when they carry their axe. They are also on horse-back and are somewhat fast and have great stamina.

The Druzhina are the cream of the crop for me. I got my first recruitement of them within the first 6 or so turns; they are Russia's heavy cavalry for the early age. They are descendents of the Vikings when they settled in the area and wield the traditional heavy battle axe.