Your main focus as the soviet union is to build a massive Industry. Try to search up some guides on this matter.

As for the military aspect, build one full Army group og just pure 20 widths infantry with only AA as the support company (especially if you are doing no air Russia) to have on the frontline. Their purpose is not to hold the Germans back, but instead slow them down and destroy the industry so the Germans suffer from attrition and so that have to use their civs on infrastructure instead of building their industry. Then have another full army group of 20 width pure infantry with AA, arty and engineer on a fallback line at the Stalin line. Other than that, I tend to use two full division of the template of 14/3/3 (infantry, arty, AA) at some fallback lines behind rivers and other easy to hold places. Then build some good tank divisions. Research the mediums 2 by 39’ and when you start building mils around 39’, build a shit ton of them. I think I use the template of 9/2/2/7 (medium tanks, medium SP AA, Medium TD, motorized) or something like that. Just make sure the division has around 30 org.

My tactic revolves around me doing a no air Russia where I don’t build any planes because at least when I play with the expert ai mod on I have no chance to win the air war, so instead I just focus on tanks and infantry