I tend to play the cheaper, most useful reinforcement card when I can. I tried to maintain my Luftwaffe at a higher number, but losses to flak keep the number down. I only play infantry when I have a beat up corp on priority, so that it can build back up to full strength. The panzer card I play when its cheaper then the other ones.
After a couple months of fighting, the most needed replacements on my front would be (by far) Dive Bombers and Fighters. Infantry would be next, with a bunch of divisions at half strength....most are hurt to some degree.
My tanks are in fairly good shape, as they only seem to attack with card support, and in good numbers. Or are chasing the enemy across the map as he withdraws.
Artillery is looking pretty good in my infantry, but then, I disbanded all my artillery regiments. Which also allowed me to motorize a few infantry divisions.
Engineers....I took a couple cards as they were cheap, to build a couple extra engineer regiments....because bridge bombing is a big part of our game.
Never looked at AT guns or Flak, so I don't know about them.
“My logisticians are a humorless lot … they know if my campaign fails, they are the first ones I will slay.” – Alexander the Great