You should watch some of Adam’s Germany plans in League games. He has some nefarious orders including bringing the fleet around into the Med to prevent subs from convoy raiding. The small fleet is also sufficient to take Gibraltar on the journey there. Other people use a limited Axis fleet to convoy raid the UK.
After G1, focus on taking Moscow or heading to the oilfields. The time is ticking to get the Axis income close to the Allied income. I have seen too many people lose as Axis because Germany gets in a fleet building competition with the United States.