Do nothing at all after 1931. Everything militarily that they did made their strategic situation worse. Bogged down in China, army beaten by the Soviets, severely damaging relations with the US. No benefit at all for all those problems. They had no real military threat and all the solutions to their economic problems just exacerbated them. If they do nothing they can end up being the big bother to all the Asian colonies of European masters who have fallen to the Germans. They maybe could even just purchase some from Dutch or Belgians who needs it for the governments in exile or get a some deal where they administer it. Even if they invade during 40-41 with no China war they can go in and set up local native governments that would be very favorable to Japan. No European power can stop them during this time and setting up native independent governments prevents US embargo and if the US does so what those countries that are established are trading with Japan the liberator no the conqueror. They same islands they go for for after Pearl Harbor that have oil and rubber etc are theirs for much less cost politically ,military, and manpower wise. After a Nazi defeat they are a bulkwork agains the spread of Communism is Asia and the US probably supports them as we did dictatorship during the Cold War. Of all the flaws the Axis powers had the main one in terms of victory or defeat is they didn’t think or plan strategically on the whole or as individual states. They planned to win battles or campaigns but not a war. They planned to solve a problem but not look at the whole situation