lets look at the ways Axis can win.
1 Take out the US
2 Take out the UK
3 Take out Russia
1 Taking out the US is all but impossible except for rare circumstances so I would recommend forgetting about this other than learning what the rare circumstances are so they can be capitalized on.
2 Taking out the UK is vastly easier than taking out the US; however this can bee seen coming and requires Germany to invest in Naval units which can be countered by the Allies. Also other than taking the UK’s distant territories Japan is left out of this fight so again I would recommend this as a situational explotation.
3 Lastly that leaves us with what the majority of the games are, Axis elimination of Russia.
That means that smashing Russia flat is the Axis’s primary concern. Grabbing Africa and scattered territories are entirely secondary. Protecting non-vital Axis units and territories is also secondary. With that in mind invest no more in Africa than it takes to eliminate the UK units in Egypt that need to go round one. If Germany can grab extra African territories on round 2 great, if not don’t worry about it. Both German fleets are weak and time is against them. I would recomend getting what you can out of them and then writing them off. So on round one Germany purchases land units for Russia and Japan purchases transports to send 8 units from Japan per turn to the main land. Once Japan has this set up then they can spend the resources to expand to the far flung territories but do not loose site of what the goal is smash Russia as fast as possible.