Tips and tactics for the USSR (Hearts of Iron 4)

I play for the Soviet Union, because I play for the first time I want to hear advice and tactics from the players, not from Google (learning in the game is dreary and incomprehensible, I figured out the basics, I turned on the historical mode, and then I get confused in diplomacy and construction). I want to build something within the borders of the USSR, preferably avoiding participation in wars. What to research / build / produce? How and with whom to conduct diplomacy? Where is the best place to deploy the army? How to avoid participating in the war? Where to spend resources?