The question of a german naval build arises only in the context of the british naval built. The problem is not, that germany has a navy but rather that the UK has none. As pointswise bombers are the most potent naval attack vehicle and can also be deployed at land, I advocate the buildup of a strong bomber force.
Still this requires the commitment of resources germany does not have at the start of game. As IMHO the optimal attack plan is to whipe out the whole royal navy, only sparing the destroyer and transport in front of the american coast (SZ9) there should be no problem - but there is. With only one carrier, one destroyer, one transport and one sub, the UK has a fleet that could start attacking germany directly where with no german fleet built the cruiser and transport have been whiped out.
Now lets assume that germany lost one fighter in G1 and built one bomber.
The german strikeforce would therefore consist of 44333.
The british fleet defence would be 44222 plus 1 additional livepoint.
So in the event of an german attack, the whole! german airforce would be lost, and the brits would still retain their
transports.
This leaves you with only two options (if you at least want to be able to contest the british fleet): Build more aircraft or build more ships.
Now the building of 3! fighters will keep your coasts free of british transports but can you really afford to spend 30 of your 31 IPCs in G1 on aircraft alone? Or are you prefering a two bomber 24 IPC solution, where one! lucky additional british hit in round one could ruin your attack? Still the building of one additional destroyer or two instead of a transport and its load would further reverse the equations.
With the base of only one cruiser (i assume the germans used the sub to kill the destroyer together with one fighter) the germans have a better base than the brit who only starts with one destroyer but who can afford to spend his whole budget on naval units.
This places the german in a peculiar place. Clearly the strategy must be to delay the attack on the german navy until B2 to conserve resources for round 1. Therefore a naval built is needed that is cheap, but that also is enough to repel the bomber and the two fighters and at best also has an attack potential that helps destroying the british fleet in combination with aircraft. That means, germany needs another surface anti-air vessel that helps keep the british aircraft away and probably some submarines - driving the price further up. Now lets test some german builts:
The british strikeforce would therefore consist of 433.
The german fleet defence:
Cruiser, destroyer, 2 subs: 32 and 2 livepoints. (20 IPC)(too weak)
Cruiser, aircraft carrier, 1 sub: 432 and 1 livepoint (20 IPC)(one fighter landed)
Crusier, battleship: 43 and 1 livepoint (20 IPC)(too weak - but might work)
Cruiser, 2 Destroyer, 1 sub: 322 and 1 livepoint. (22 IPC)(too weak - but might work)
Cruiser, 2 Destroyer, 2 subs: 322 and 2 livepoints (28 IPC)(too expensive)
(Only the fighter that attacked seazone 6 together with the submarine can land on the carrier. Other attack pattern will only allow more british ships to survive)
Only the carrier submarine combo or the battleship can survive a british air attack.
Now lets assume the british didnt attack affraid of loosing too many aircraft (although the cruiser battleship combo is still a little bit weak)
Now lets assume that germany lost one fighter in G1 and built one carrier and one submarine.
The german strikeforce would therefore consist of 4333321.
The british fleet defence would be 442221.
Probably one german bomber would survive
Now lets assume that germany lost one fighter in G1 and built one battleship.
The german strikeforce would therefore consist of 443333 plus 1 additional livepoint.
The british fleet defence would be 442221.
Probably the german battleship and one bomber or one bomber and one fighter would survive
Now lets assume that germany lost one fighter in G1 and built two destroyers and one submarine.
The german strikeforce would therefore consist of 43333222.
The british fleet defence would be 442221.
Probably the german bomber and one or two fighters would survive
Under these circumstances attacking the lone battleship / destroyers and sub and building one additonal fighter instead of the sub should be the british course of action. For those who love the risk, the battleship is the best offensive opportunity against the british fleet with least losses in counterattack.
For hardcore gaming I recommend the two destroyers and sub or the carrier sub combo as its weaker on the offence but better on defense. The carrier sub combo ist the real defence monster, but the destroyers and the sub has more offensive potential. The real question is where to draw the line in cost cutting.
Now i will try these builts against the max british fleet defence with no landing force or transports:
UK built: 1 Carrier, 2 destroyers, 2 submarines
Now lets assume that germany lost one fighter in G1 and built one carrier and one submarine.
The german strikeforce would therefore consist of 4333321.
The british fleet defence would be 44222211.
Total whipeout / the lone transport survives
Now lets assume that germany lost one fighter in G1 and built one battleship.
The german strikeforce would therefore consist of 443333 plus 1 additional livepoint.
The british fleet defence would be 44222211.
Total whipeout / the lone transport survives
Now lets assume that germany lost one fighter in G1 and built two destroyers and one submarine.
The german strikeforce would therefore consist of 43333222.
The british fleet defence would be 44222211.
Probably the german bomber would survive
SUMMARY
The german battleship should it survive B1 will totally establish total german dominance over the french coasts at the risk of losing it in B1 whereas the carrier sub combo forces the british to go all out on ships to stop. The two destroyer one sub built is a more expensive but balanced built. Eighter built ist a severe theat to any british ships and will probably force the UK to move its ships away and hide them behind GB for a B2 built preventing B1 landings I also like the 2 sub strategy of Funcionetta as an even cheaper built. Depending on UK airforce further german built of 1 submarine and solid airforce should continue keep the royal navy at bay. - But rotten luck cant be calculated.