The key to defending for the allies to to keep Lenningrad. the 12$ should be spent on 4 infantry to defend the city. If either Lenningrad or Vyborg stand at the end of the first German turn, the allies can use british fighters to attack and destroy the German fleet. So, the 12$ should be spent on a transport for the baltic so the allies have to fight for Lenningrad.
Isolating and weakening German spearheads is key to victory!
I agree that it is important that Russia take a defensive stance against Germany. But the Russian player must take advantage of the sheer size of the Russia territory on the game board. If the Germans go south or go for the center(Belorussia) they risk isolating themselves from the front. Russia must counter attack no matter how big the size of the german spearhead. That is why it is imporant to build a small amout of offensive units like TANKS every turn for the Russians. One tank per Russian turn would give the russians about 6 tanks in the third turn. Using the 6 tanks wisely with infantry and artillery, you could repel any major german thrust into the 3 major provinces of the front lines in russia. Remember that time is on the allies side, all russia has to do is hold out, which requires deflecting and dispersing the german attacks. Also try to retreat your tanks from the battle, you may have not taken the territory but you have heavily weakened the German spearhead. An experienced German player knows there is no point thrusting into the heart of Russia with a medium sized force. With this German mindset, the Russians can use that all or nothing attitude against the Germans. DO NOT use tanks on the front, they are worth more than gold to the Russians, only use them in counterattacks with lots of infantry. Keep the tanks on the secondary provinces of Russia, so they can reach the 3 front lines countries of Ukraine, Belorussia, and Leningrad. The longer Russia holdouts the more offensive units it will possess(fighters from allies, and self built tanks). You can use these offensive units in an defensive role in your defense of Russia.
one of my russian strategies is to feep the germans bottled up in east poland/baltic states/ukraine as long as possible, and then i retreat to turkestan w/ almost all of my men. if they try to go north to russia, i counter attack. if the go down the middle to bellorussia, i counterattack. if they go south to caucasus or stalingrad, then i counterattack. usually by this point ( turn 3 or 4) i have beaten the germans in the far north, and i have at least 4 russian fighters and 3 bombers, 3 or 4 tanks, the rest of my infantry that i retreated with + all the infantry i have bought so far, plus the 8 or 9 artillery i have to counterattack with.