Did they build their Carrier in the Med or sz5?
For me the Med is a more viable option, because it allows you to bring a fighter into the destroyer attack off suez.
You can still field 9 infantry if you’re not really after Sea Lion but just want to make things hard on the Royal Airforce or Africa by expanding the German fleet. Or I have seen a destroyer, 5 inf and artillery piece. Or 1 carrier, 1 destroyer, 1 transport out of the Italy factory with the rest on whatever.
Med fleet is fairly useless if sz 16 is closed though. So that could factor into it.
Sea Lion posturing for me is more about maintaining fleet parity and screwing over India than actually being able to take London.
Usually I go on the ground with Artillery and Tanks, or in the Air with bombers and fighters, rather than by sea with expensive ships. But I have seen players pull it off. I’d still say it’s very difficult though.
is there a standard G1 purchase to achieve this no matter what Russia does R1?
All you really have to do to prevent it is land your Russian fighters in Archangel on R1 instead of Moscow or Caucasus. Even landing 1 Yak in Archangel, would be enough to deter a transport buy for me with Germany. I think G2/G3 chances only work if Allies make a mistake.
Then again, it depends if what you’re trying to achieve is just a German fleet that can make UK spend on defense, or a German fleet that can actually invade and take London in the first few rounds of gameplay. The former is doable, the latter is kind of a pipe dream. Soon as you start buying transports and carriers you essentially reverse roles with UK/USA. Now they are the ones who can just buy a ton of bombers to wipe you, whereas usually it’s the other way round haha.
Here’s a thing you can try that is relatively inexpensive, just buy a lone Baltic destroyer. Sometimes this is enough to deter the Baltic air strike, and it only costs 8 ipcs. Then you can decide on G2 whether further investment in sz5 is workable or not, without giving up your position against Russia in the process.