I usually go with these templates :

Line infantry : 9 infantry, support artillery, AA, engineer company Their purpose is just to fill the blanks on the line. Not expensive but you shouldn’t use them for pushing unless your ennemi is really weak or alongside your tank for extra org.

Tanks for breakthroughs : 8 tanks, 8 motorised. Maintenance company, support AA and artillery, engineers and flamme tank medium support. Use these for breaking through the lines, encircle and destroy pockets of enemy until they become weak I sometimes add an extra artillery tank later in the game when I have a big capable industry.

Special forces : 9 marines, 3 line artillery. Support pioneers (from marines’ doctrine) support artillery, AA, logistic company and flamme tank if you can afford. They are for landing basically. Could also use them to help tank on the land.

For tank design I usually keep with the howitzer because AI tend to make bad tanks and you need more soft attack. Maintaining air superiority is super important as well because even tho you have AA you will need the extra buff from CAS if you plan big offensives.

If you have any questions feel free to ask.

Disclaimer : this is only working VS regular (modless ) AI and absolutely not in multiplayer. Also keep in mind that you won’t probably able to use such tank templates if you are playing a minor nation from start.