1. J3. Gives you time to prepare your transports to attack any territory you want them to. It also is the turn that America enters the war, so you’re really only allowing them to move out of their own territories, which is outweighed by the initiative you gain as Japan
2. I buy 2 on the first round, so I have 5, and then maybe 1 later on. I am always willing to sacrifice a transport for control of a DEI, as long as the allies lack any transports to get it back. So once I have the DEIs, I only have 2-3 transports in circulation.
3. Minor IC in Shanghai territory, build 3 mechs a turn for use in China and India. Naval Base In Hainan, because I can drop any troops from Japan off there, and then have the option to move them toward India, or load them back on the transports that brought them there and attack any number of important Islands.
4. In order of importance: Borneo, Philippines, Java, Solomon Islands, and Malay. Borneo, Java, and Malay because they earn you lots of money and reduce the Allied income. Solomon Islands, because it gets rid of both ANZAC NOs with one move, and its hard for them to get it back. Philippines, because it reduces American Income and contains an important naval and air base.
5. 36, if you have a naval base in Hainan, you can hit all the important mainland territories (Calcutta), all the DEIs, the Caroline Islands, Japan, and part of Australia. 35, if you control the Philippines, although you can’t India from there.