I'm currently playing a game as the Soviets as well.
I left the affairs of the world alone until I could modernise my army and replenish my troops. I sought the unholy alliance and failed to convince the Germans that it was in their best interest to accept(oh how they would soon understand).
The winter war was a quick success and I soon annexed and painted Finland red. I pulled all my forces to the German border and watched their assault of Europe closely. Poland had already fallen and had been divided, I took control of the baltic states. In early 1940, Germany DOW'd Denmark, Norway, Belgium, Netherlands and Luxembourg and began their historical march for France.
As German forces began leaving the Soviet border my small airforce of a dozen fighters, 8 Tactical bombers and 6 CAS became fully ready and were deployed to newly built airfields just east of the border.
In mid-June 1940, The Germans had rolled over Denmark, the Netherlands, and Belgium, Luxembourg and were beginning to march into France. They had also begun landings on Norway. I DOW'd Germany and took advantage of the weakened German border. I quickly gained territory and soon most of Poland was under my control. I turned my attention to the German allies in Hungary and Slovakia and soon their territories belonged to the Soviets. Italy joined the Axis soon after and took advantage of under-defended British and French Africa. The Germans push into France and Norway was stalled as they pulled forces East to address the advancing Soviets. By August I had managed to conquer all of Poland, Hungary, Czechoslovakia.
I had just taken Stettin when Romania joins the Axis and I have virtually no forces in place to defend against them. I move a few infantry divisions towards Odessa, hoping to get there before the Romanian forces overrun. But I failed, the Romanians quickly expanded on all sides and only the few infantry divisions to defend and attack. No new forces were due to arrive until October but I decided to leave the Romanian army to its attacks while I pushed for Berlin. The Romanians had pentrated to Kiev and were beginning to expand North-west, threatening to cut off my own forces against the Germans. I was forced to sacrifice several of my German attackers to deal with the Romanians.
By the end of September I had forced the Romanians back to Romanian territory and began an all sides attack on their land. I was soon in control of all of South Romania and soon they came to my side as a puppet.
Meanwhile I had taken Berlin but my advance had stagnated due to heavy German forces in the North. I forced my way south and penetrated to Usti and Munich, but now I was dealing with Germans that were protected by various fortresses. My initial plan was to completely overrun Germany before France was booted from the continent but I had failed, as Bordeaux, the last French holding fell to the Nazis. I managed to surround the Germans several times in Northern Germany and by December Northern and Southern Germany belonged to me. They still held a few German territories, specifically those that border France and Belgium. With winter settled in I had no choice but to hold off my advance into Denmark as a significant Italian and German forced were blocking access. Instead I filled in the gaps in my front with fresh infantry and moved my forces that had been attacking Romania into the Italian border. I took Milan and Venice from the Italians before being stalemated by further advance by a large amount fo Italian and German forces.
By March of 1941, Italy was being defeated in Africa and Germany had been successful in defeating Norway. I was forced to send a handful of soldiers to Northern Finland to attack the Germans there. I begun taking the last German territory and swept through Denmark with only Copenhagen remaining with a German naval force providing protection.
And this is where I am now, it is June 1941. All of Germany belongs to me, I've pentrated half of Norway, I've had moderate success taking new territory in Italy and I can advance no further West as it would take my into the allies territory. In the far east Japan has almost totally overrun National China but my Chinese Comrades are still intact.
I'm considering my next options. I will definitely attempt to finish off Italy and take Norway and copenhagen from Germany. Then I have a few options. I could declare war on the allies and take the rest of Europe for myself, but this would require an immediate invasion of Britain which I'm not sure I'm capable of at this point. Or I could provide a good defence for my new Borders and send my offensive force east to attack Japan and possibly make an alliance with Communist China.