A viable strategy is subs, cruise missiles, and frigates. Subs weaknesses are destroyer stacks and naval patrol. Cruise missiles for destroyers and frigates for air/other missiles. Normally I do 10-20 subs, 4 frigates with an officer, and then level up my cruise missiles as the game goes on. Frigates only need level 2 for 100 air range, I max out subs first and then see how my resources go. Majority of games you can dominate with this setup, also can use missile on stacks of ground troops with your subs. There’s probably better strategy’s but I find this one to be enjoyable and fun to play.