As promised, my Russian strategy:
There are 2 routes, and which one you use is dependent on Germany’s plan.
Assuming Barbarossa, as that is the easiest:
All inf. Perhaps 1 art or 1 arm, but inf is your purchase. You can either fall back all the way to Moscow or defend all your IC’s, but you don’t want to be fighting major battles with Germany in any other territories unless you get him exposed.
If there is Sealion, you still want 6 inf. per turn in Ukr/Leningrad (sometimes I’ll put an art or 2 in there as well), but the rest should be on mech/tanks in Moscow. Put all your forces up front (save some in Leningrad in case of amphibious assault) and be ready to defend/attack Germany along Rom/Hun/Pol.