Probably straight Barbarossa. G2 declaration of war on Russia, a G1 purchase of either 2 bombers/1 sub (to somewhat fake sealion and use bombers for Barbarossa), 6 art/1 tank, or some other buy that would be very useful in the eastern front. After G2, buy mostly mechs/tanks/planes so they can get to the front lines quickly.
Also on G1, taking out SZ 110+111 fleets from Britain are important, though taking Normandy/Southern France + France, Yugoslavia, or even Bulgaria are not really needed. You could “ping-pong” your units from Greater Southern Germany to Romania by moving one infantry from Romania and your 6 infantry 2 artillery (and maybe a fighter or tactical bomber to give less infantry for Italy to kill) from GSG and after one round of combat moving them all to Romania. That way they can all attack Bessarabia on turn 2.
Italy could send can-openers, but a 100% German push on Russia should take Moscow on G5/6/7, so Italy could focus on North Africa, Gibraltar, and/or the Middle East, as they normally do. Taking Greece, Southern France, and Gibraltar I1 and clearing the Med of ships (Germany can actually spare a fighter+tac bomber from West Germany to attack the French fleet off the coast of Southern France so Italy gets their bonuses more easily, which is what I normally do on G1) would give Italy 25+ IPCs to spend on I2, which would give them a lot of momentum. Though this is harder if the British do the Taranto raid (in that case, I would recommend not scrambling unless you have really good reason to).