As someone who has played large scale campaigns and has one on-going, I can speak with some experience:
If you want to field a larger force, I suggest not more than a battalion of armor and a battalion of infantry. Ideally take either a couple platoons or a company of engineers to help your tanks out in close quarters and in assaults. They also make for a very strong reaction force if you buy some tank destroyers/stug's.
It also follows the usual German doctrine of assigning a tank company to support a Panzergrenadier company, etc. I buy transports out of support points to fit most of this in; I am not the norm! If you want something more sane, do a Panzergrenadier battalion with transports and a single Panzer company. I tend to push the upper edges of what is playable, but acknowledge it is not really what the game is ideally based around.
Example OOB:
3x Panzergrenadier kp (with built in mortars and machineguns, otherwise buy a seperate platoon and attach it during deployment)
3x Panzer kp (1 Medium, 2 "Light", as per early war TO/E)
1x Panzer-Pionier kp
2-3 Artillery batteries
1 Infantry Gun company / Heavy Mortar battery
2-3 FlaK batteries / Self-propelled being preferred
If I buy scouts, I buy them out of the support points. Armored cars are fun but mostly just tend to do "Recon by death", so I find it more useful to probe with my infantry who can take some hits. With enough experience they will do about as well as the scouts anyways.