Protect moving groups against ground attack planes with fighters, not mobile anti-aircraft. Do not put tanks in the first line of a beachhead defense force unless you just want to provide targets for enemy ships. Pull your tanks back and keep them as a reaction for against breakthroughs. If you are defending a small area, don't build tanks, build gun turrets and mobile units with long range weapons. If you are facing a foe without much air capacity, you can use scouts instead of escorts to provide information for gunboats and missile cruisers.
Submarines can be devastating to a sea-based power.
Corvettes and-Ground Attack Planes dedicated to protecting shipyards and docks and sea mines may seem like a needless expense until these facilities start blowing up in your back yard. Of course, a sea mine field is also a good investment. Mine fields are always useful as a protection. The best use of minefields is in front of a position that can be protected by infantry and scouts to take care of surveyors and minelayers. Infiltrators are always useful.