I usually build 2 fabrics on mainland, because Japan always loses its transports, and its immobile to do any good if you don’t have units on mainland. After that i spend 30 IPC on tanks (2 x 3 tanks) or maybe 2 x (2 tanks + 1 inf)
And the just kill India and run for soviet. Preferably both at the same time.
The faster you can put pressure soviet the faster soviet will put money on the Asian side of the instead of in Europe. This gives Germany some room to grow.

Also Germany should always have airplanes ready to kill small tropes that soviet use for stopping japan to blitz Moscow. So then japan can blitz Moscow.

A friend and I almost broke the game by putting almost all German money on recherche. To get long range for the air plains.
Then you can really easy take London the first turn. And with that start its almost impossible to lose.
But this is almost ruining the fun.