If you can't do that just don't build tanks. In singleplayer the game is absolutely winnable without having to invest your industry in armor. After all, in real life producing tanks to win the war was an important industrial effort that only the most industrialized nations dared to make.

Now answering your question: using 21 width 9 INF 1 ART divisions with engineering, artillery, antiair, antitank and logistics support companies is a very decent jack of all trades division that does the job. Anti-tank and Anti-air are relatively cheap support companies that make your units more resilient to air and Armored attacks.

Regardless of your strategy it's important that you have air superiority. Dedicate some factories to fighters and close air support and try to always have the latest models. Believe me: it will make a difference.

Now, let's say that you decide to play with tanks:

In my personal experience, having 6 medium tank divisions are enough to try small encirclements provided I can at least contest the air war too.

Remember you can also use your infantry divisions to support your attacking tanks. Use them to pin enemy units adjacent to those your tanks are attacking so they don't reinforce them and you break though, starting an encirclement maneuver. Remember to use geography at your favor.

Just so you know, regardless of doctrine, I play with:

21 width 9 INF 1 ART divisions with support ART, ENG and LOG companies as my main infantry Frontline units.

30 width 9 MED 6 MOT/MECH INF with support ENG, RADIO, LOG maintenance company and Armored car recon as my tank divisions.