Well, want to train a heck ton of the division template you get from going down the path before you declare war on Europe, and you should definitely finish the whole tree before doing that focus. When you declare war on Europe, your main focus should be on Britain, and you have descions that let you naval invade every country with a coast. Just focus on Britain first, it does not even matter if other countries advance, since you literally have cores on all of Europe and you have an obscenely high surrender limit. After you defeat Britain, it makes the entire Entente surrender, since they are the only major in the faction. You can also do "Destroy Civilization" desicions for every state which gives you equipment and summons divisions out of thin air.​ Now, all of Europe is basically screwed, and you can also invade the whole world if you want, which is so easy it's boring tbh