Best way to learn

Check out the sidebar and in particular the Starter's Guide.

My suggestions (which certainly aren't definitive):

Get a textbook. I recommend Genki, but you can use any standard Japanese textbook. Just pick one and stick with it. Read a lesson, do the exercises, and then create exercises for yourself. If you can't afford a textbook (or other resources mentioned here) check your local library or search online. There are lots of ways to get these resources for free.

Pick either WaniKani or the Kodansha Kanji Learner's Course (KKLC) for learning Kanji. WaniKani is a web app that does all the hard work for you (but requires a monthly subscription). KKLC is a textbook that'll teach you everything you need to know about kanji, but you'll need to manage your own flashcard system, probably using Anki.

Learn how to use flashcards. Look up the phrase "spaced repetition" and learn what it means. You should probably learn how to use Anki, Memrise, or any of the other automated flashcard services available online. But of course you could also just use old fashioned pen and paper cards.

Learn about online resources for practicing Japanese. HelloTalk (App Store, Play Store) is like a social network for language learning. You can make posts and have people correct your grammar, and make friends that you can practice Japanese with. HiNative is a website and app where you can get language learning help from and ask questions to native speakers of Japanese. iTalki is a website for finding a tutor, but they've got a good journal section where you can write small essays in Japanese and get them corrected by other users.

Don't jump between resources. After you pick a resource, see it through to the end. Don't waste time switching back and forth between different language learning methods or materials.

Practice every day, even if it is for a short amount of time. Practicing seven days a week for 15 minutes is much more effective for your learning than practicing for three hours on Saturday.

Consider getting a tutor or taking a class if available. Learning Japanese is enough of a pain without also needing to teach yourself how to teach yourself something.

Here, how about you browse r/learnjapanese and look at other recent posts or the wiki!