There isn’t one.
I suppose I could end the post there, and possibly that kind of brevity would make us all happy, but, somehow, I just can’t do it.
The point is that you and I are different. Do we have things in common? I’m sure we do, what with us both being human beings and all (apologies to any aliens or sentient aardvarks who happen to be reading this post), so there are some good study ideas that we could both benefit from, but they’ve been listed ad nauseam in various posts here and in lots of other places.
But what you shouldn’t do is waste a bunch of time looking for the best method out there, because do you know what you could have been doing with all that time instead? You could have been studying Japanese!
Sometime people waste so much time looking for the right course or the right book or the right teacher that they end up wasting a ton of time. Grab a book, grab an app, pick a teacher at random, just get started. As you go, you’ll figure out how to do things better. If you decided to look at a different book, then do, but keep studying with the first one in the meantime. If you’ve decided the app or website you’re using is okay but not great, then look a around, but keep using the app in the meantime.
Just as an example, you could broadly divide the book users into three categories: Those that love Genki, those that love Minna No Nihongo and those that love some other book. And, you know what? They’re all right. The book they are using and love is definitely the best book, because they’re using it and learning, and that’s the key.
You can spend so much time looking for resources and that you don’t learn a thing. Just jump into the pool and start swimming. The best book/app/website/tutor/teacher/study method will come along eventually is whichever one works for you, but some people act like finding the best is their goal.
My goal is learning Japanese. I use some techniques and apps and websites that I didn’t know about when I started, and that’s fine because I spent more time studying than I did looking for new study tools.