The Russian problem seems really to exist early in the game as you have no economy to speak of and weak infantry options. I play VH battle/H campaign and decided to 'turtle' initially. This meant I took neither Kiev ( a trouble magnet in my first attempt as Russia ) nor Stockholm ( in order not to have a land front against the Danes), I also avoided the eastern extreme of the map, Moscow and Ryazan mark my eastern extremities. My focus has been largely in kick starting the Russian economy whilst obtaining an alliance with HRE to sandwich Poland.

Militarily I have so far focussed on Kazaks and Boyars sons for almost the entirety of my field armies, this has allowed me mobility to deal with rebels hindering trade and threatening cities and also Polish incursions whilst retraining at my twin castles of Smolensk and Ryazan can be established quickly because of the mobility of the units.

I have avoided war with all but the Poles so far and that war has really been little more than an a series of extremely one sided border skirmishes. This has allowed me to negotiate a ceasefire with the Poles after a series of crushing victories which cost them 12000 florins plus 1000 a year tribute for 5 years ( funding a fortress upgrade amongst others that I could not afford otherwise ). I fully expect a major offensive towards Vilnius sometime soon as Polish armies are beginning to appear South of that location but am happy as I can now afford a larger military, meaning an infantry force to assault and garrison newly taken territory. The plan now is to wait on the Polish offense, fight their armies in the open using horse archers then move on their fortresses at Halech and Thorn initially seiging with cavalry but adding infantry in to allow me to assault if necessary. With a half stack garrison in each plus missile cavalry forces outside I believe I should be able to hold these new positions which will also likely allow me the jump in technology to allow me a military to compete.