Basic build is a standard 5 tier one units, e.g. 4 grens, 1 MG42 and healing bunker.If your facing USF, place two tellers if you can early on tight maps. On open maps, if they go liutenant, don't bother with this build as you need fast tech vs the inevitable light vehicle. Vs anything else..
Don't tech, wait for 3 cps and call in two Mechanised assault groups. You don't actually float that much I find in the very early game with reinforcement costs and the healing bunker.
By not teching, your saving essentially 320 mp and 60 fuel, once you include the costs of the t2 building. Way I see it, that is the cost of the two 250 halftracks covered, as they work out as 150 mp and 30 fuel per one. So 300 mp and 60 fuel combined for both of them. Two Pgren squads is allot of AI and you can get access to the Shrecks without teching. This changed at some point, as originally when the doctrine came out, you needed the tech to upragde the assault groups.
So your saving on the nasty sunk costs of Ostheer tech in the early game, in favor of more units quicker. Pretty simple deductive logic from here, if they go for a light-medium armour, upgrade shrecks as need be (2 does vs t-70/Stuart/Greyhound, 4 is needed vs medium tanks) and use the halftracks to flank or Pgrens in cover/buildings to play defensive. If your far behind in fuel (you'll know, you need paks, although tbh its a bit all in, if the two mech groups did not swing the early game in your favour, then your probably fecked anyways..)
If they save for calls ins, use pios with flamers in the halftracks and keep Pgrens vanilla. If its call in tanks before 11 cps, get Shrecks at an approximate time you think the tanks will hit and lay a teller or two (since you have no LMGS)
Either way, a Stug E is always useful to throw into the mix at 6 cps and your ofc gonna get a Tiger once available (11 cps). After that, you might want to tech to get access to a PAK and LMG upgrades for the grens.