Slitherine

What would you folks suggest is the best areas of research and techs for the Germans in GS game?

I usually build labs in the following priority.
1939
1. General (september 1. focus industry)
2. Infantry (september 21)
3. Air (september 21 balanced in the beginning and then focus dogfight when you can get strategic operations tech 1 and dogfight tech 1 at the same turn)
4. Armor (october 11)
5. Naval (october 31 focus submarine)

1940:
6. General (january)
7. Armor (february)
8. Infantry (february)
9. Air (march)

1941:
10. Infantry (january)
11. Armor (january)
12. Air (january)
13. General (when tech 3 industry is available)

It's possible to build a second naval lab in 1940 and sell it again in 1941-1942 so you can build the third general lab. That can be smart if you intend to build a huge sub force and want better subs sooner.

Research Armor second if you're playing the AI. Germany can get strong enough tanks to cut the Soviets to pieces within a year if you're determined enough.

Stauffenberg, after 1941 you don't build labs anymore? (pardon me my stupid question perhaps but i'm really a neophyte here)

Then you have maxed out your lab capacity (13). Later in the game you can get industry tech 5 and that means you increase to max labs 14. Then you can build a fourth lab in e. g. armor or infantry.