It is best to buy Mechs and can open and support Germany on the East Front. If the opportunity arises, and the U.K. and US player allow it, buy a DD to keep your convoying down. Don’t make it easy for the Allies to deny you income. German Fts often have to park in Rome to scramble to sink Subs.
Playing Italy is about bothering the Allies, forcing them to spend in the Med, when they want to go East, towards the ME.