The game works best with 4-5 experienced players.
1/ Germany Italy
2/ Japan
3/ Both UKs, and france
3/4 and or Russia give it to either ally or your fifth guy
5/ US China ANZAC
Who cares; France
(US and Anzac) and (Germany and Italy) need to work as a lockstep team to ensure victory. If you split either of these sets, it makes coordination and victory much more difficult.
ANZAC
Italy
UK Pac
China
France
None of these make ideal choices for new players; they go late in the turn, they have limited income, and the income they do have needs to be carefully coordinated with the ‘parent’ power’s strategy in mind. There is not much to do with the bottom two, so not really worth being their own player.
If you do have 8 players, then you have to ask whether having 2 tables (playing same or different games) or splitting the game into its two halves and playing just in the same room, not on the same map would be easier. If you do this, there is a lower chance of boredom and the total play time is less, but the disadvantage is that you don’t have the awesome “battle royale” that all the players get to engage in. You could, if you are still learning, assign the 4 newest players to be “adjunct” leaders to the main powers (listed at top), and either player could make decisions/roll dice/move pieces/respond to questions. However, the main player would still want to call the buys and attacks, most likely.