I generally go with one of three options…
8 INF if I’m nervous, or planning on playing defensively…
5 INF, 1 ART, 1 ARM if I want a more balanced buy…
or 3 INF, 3 ARM if I plan on pushing foward…
Our group plays with NAs though, so the build can vary quite a bit (especially with the Non-Agression treaty! :-D )
As for navy, I’ve contemplated an R1 buy of an AC and a TRAN, moving both Russian fighters to the Carrier…could help keep the Nazis out of Egypt, and will certainly allow for an easy retake, plus it gives the Luftwaffe a LOT to deal with on G1…some of those planes will fall.
Worth the ground your going to have to give up as Russia to ensure that Britain holds most of Africa until Japan tries something?