So far the most cost effective way seems to be 3 BB + 2-3 CVL + ~6 CL. Pack all units except for your subs into the Kriegsmarine and sink the British navy.
Subs are also possible, but require more leadership for research. In addition, to produce subs en masse you need quite some MP and fuel. Plus: IC wise BB also seem to be better (BB 4387,5 ICd vs Sub 1080 ICd), but this does not include escorts.
So either go subs or BB / BB+CVL. If you go subs, make sure you have electric torpedo ready around 39 - its doable.
Subs are also possible, but require more leadership for research. In addition, to produce subs en masse you need quite some MP and fuel. Plus: IC wise BB also seem to be better (BB 4387,5 ICd vs Sub 1080 ICd), but this does not include escorts.
So either go subs or BB / BB+CVL. If you go subs, make sure you have electric torpedo ready around 39 - its doable.