G1 Major in Romania, G2 9-10 artillery, G3 10 artillery, G4 10 combo of men and or artillery, G5 Either another combo to push in anther direction or 10 mech to catch your advancing stack that heads for Leningrad. Russia is dreaming if they think they can match it. Also make sure that you NEVER allow them to get their 5$ bonus, it is enough to stop with a single sub.
This build has been an absolute recipe for pure Soviet crushing strategy. Maximizes your bonuses and allows for you to build up some subs as well to fend off UK and US when they start thinking about coming back to Europe. The in depth rounded strategy would take longer but that is how I steam roll through the Soviets.
I should also mention that in Alpha set up (how we always play) Japan will always take 2 territories on J1 and a total of 5 by J2 from Russia. Having all those extra men in Manchuria and Korea are just waiting to push those Soviet Far East troops back to the interior.