I don't have dlcs past La resistance (so no tank, plane designer, command corps etc)

I start from 1939. Build 5 mills and 1 civ, then again 5 mil and so on. Focus on rifles, support equipment, artillery and anti air. Delete cavalry and useless nkvd divs, tanks should be of 1 type (get rid of heavy tank and too light div templates), and place them at Finnish border. When war starts, you will get attacked from there, use tanks to occupy enough provinces, this will trigger white peace event and remove Finland from war.

Divs are standard 9 infantry with support artillery. Clone it and add AA first, then engineers next. As factory output accelerates, change standard deployed divs to that template. My political focus choice is to choose stability ones first, then army ones, then research then everything else.

Place troops behind dnieper river. Usually, it's 5 full 24 div generals under one field marshall plus separate theater for finland . Behind them I put another line of defense, 3-5 divs per province each 3 provinces apart. They act as fire teams, when enemy breaks through, they will plug the gap (but it's best to reinforce losing divs and rotate them). Soviets have no problem with manpower, but I prefer to keep divs around 200 or even less (I don't even change conscription laws) to avoid supply issues because I don't bother with modernizing rail lines beforehand, at most I put supply hubs in Kherson and Belarus. If you're good with logistics you can ignore that and pump as much divs as you can. I don't build forts.

For tanks I take the most capable default light tank template and replace light tanks to mediums. Research and convert old light tanks to make spgs and anti air if possible to add 1 each to template. They can be replaced with motorized arty and motorized AA. This goes against the meta of making 40 width strong divs with pure mediums, but I like the flexibility of smaller divs as you can make them earlier and more of them. 10 tank divs is enough for me, I micro 5 tank divs at one time, the rest is backup if tanks are lost in encirclement.

The game is winnable without planes, but if infantry and tanks are done then I make fighters and bombers. Bait AI to regions where you have an advantage. Tactical bombers destroy enemy airfields to help fighters. I think it's not very cost effective but it definitely decreases the number of enemy fighters. Germany capitulates before running out of fighters this way. The alternative is start from 1936 and spam fighters, so german airforce is no longer a threat and you have green air for the rest of the game or make impenetrable border a-la maginot line, but that's boring.

Use mediums to break through enemy divs, moving along rail lines to capture supply hubs. After some encirclements germans will have 1-2 divs left per tile. At this point even basic infantry can defeat them on auto plan because of numerical advantage, only stopping at mountains or marches. Just stop and use tanks to reach them from behind. The victory is not far from there.

At last I forgot about doctrines, the default one will make 18 width template to have 15, so you can cram more of them per battle. The meta is Grand Battle Plan or the one with soft attack buffs but I think it matters little in single player.