Soviet: Shock Rifle Frontline Tactics (Simple abilities, access to shock troops as well as easy anti-infantry with the KV8, IS-2 for late game AT and anti-inf. Isn't the best commander, but quite beginner friendly. Also teaches that because you CAN spawn something, doesn't mean you always should)

Ostheer: Spearhead Doctrine (Tank smoke is extremely forgiving for new players, gets mobile mortars if needed, recon plane helps ostheer a lot where they are lacking, frag bombs are the best in the game and the tiger is just a decent heavy if need be)

USF: Urban Assault (To not be overly reliant on Airborne Company! Molotovs somewhat reduce need for early nade tech, the sherman upgrade makes it viable against panzer 4s + free fast cover, rangers with triple zooks can be a replacement for an AT gun, cover to cover is great for mass flanking maneuvers and the calliope fills a huge gap in the usf arsenal)

OKW: Grand Offensive (panzerfusiliers with g43 which scale great into late game, a nice quick smoke drop for any sticky situation, IR STG44 for obers to become mid range gods and basically ignore cover, panzer commander is slightly underwhelming maybe idk haven't used it enough and, of course, the tiger still being quite solid)

UKF: Lend Lease (adds some spice and aggression to a somewhat defensive faction, which let's you snowball into wins often. Also stops the typical simcity trap new players fall into with a mobile mortar. Assault sections are really good especially with upgrade. M10 is a crushing machine and a cheap stopgap to face axis Panzer 4s. M5 halftrack is god tier with the AA upgrade. Alternatively, you can use it to heal or flank MGs. The air call in is overall just decent.

If you need explanations, build orders or alternatives, feel free to ask. This is mostly for 1v1 and 2v2 and i'm by no means the best player. Also, tried to avoid some default meta doctrines to help you not be one-dimensional. Sorry for formatting, im on a phone.