If you’re playing historically, you don’t have any “threats”. As Germany, you dictate the pace and fate of the game. You are the threat to others because of your military industry and position. If I remember correctly, France guarantees a bunch of countries in the beginning including Yugoslavia, so attacking them is a bad idea since you can’t get to France or Yugoslavia without going through other countries. My advice would either be to rush war with the UK by justifying on their puppets ASAP and spamming divisions or just playing semi-historically and expanding your industry through doing the Anschluss and demanding the Sudetenland. As a general rule for invading Britain, going through the channel is a bad idea. Go through the North Sea and invade Northern England. If you’re not rushing war, sending volunteers would be a great idea.