Be friend with UK his navy can easily destroy your life and you wont need to focus africa but most of players are beginners so I dont think it will attack you. I supposed he is experienced
invade yugoslavia and greece before than others
North italy is very easy to defend against northern invaders you have support of big ships and have many mountain to slow enemy
If USA is experienced player dont forget to have good relationship with him
Ships , Anti air , artillery , anti tank , infantry , planes your best friends
Dont need to tanks. You can use armored cars
France is not important country but if they decide to create a coalition with germany , depends your experience and activity they can kill you. You should follow them at the beginning of game , if they create a coalition join them
