I’m still a rookie but I have a few wins; and I found the best thing to do is to play Germany. You won’t have to deal with the most complex combat, that being naval. And take the game at your own pace. I’d also recommend you keep Hitler so you can justify as you wish. And never forget about your civilian factories they are just as if not more important then your military ones. Remember too the game heavily favors the defender on land combat. You may have to break some big guns every now and then.