Well for Ost the most basic build order is mg 42 into 3 grens into 222 into Pak into tek into p4 this of course changes for example you have no fuel for tek you get a second pak or the enemy is dug in get a mortar or you have a tuff time against all the inf. then get a second mg. What i also like to do is skip the p4 and go for brumbär or werfer that is something i decide in game becouse of my opponents mybe they blob a lot then skip p4 if you can and go for werfer or brumbär or you are expecting an AVRE or t34/85s go for panther
So now you ask how do i know when i should get a P4 or a werfer... well what i am always checking first does the enemy have double at gun? if not P4 if so then werfer or brumbär why well your P4 gets killed and stopped from doing anything game changing. Thats something you have to pay attention
Now OKW depending if you can micro a Kubel then 1 volks into kubel into 2 more volks if not either 4 volks or 3 volks into Battelgroup tek into flak halftrack(if you have the micro for it) or mg 34 or ISG if you chose a Commander with a call in Unit you can also go for a jäger,offizier instead of the Mg what you like more into at gun then into schwere and if you have enought 1 ober if not mg, at gun, ISG... then P4 or Panther so now we come to a problem the enemy has double at gun and as OkW you would need a stuka or Lefh to hard counter those well stuka takes long to get if you didnt start with Mechaniced and Lefh is only in 2 Commanders so what i do is smoke them with my ISG or barrage them with the ISG that can help or get an infrared halftreck so you spot them and can avoid them or barrage them.
That is a little bit of the basic stuff but i also added what to do in some scenarios it all really just depens on the situation i hope i could help with this long answer if you still have questions ask or watch some youtube videos from tightrope he explains this very well
Link:
https://www.youtube.com/c/tightropegaming