If you want to learn it on your own you need to find your own way as well. Also you need to stick to it by yourself, at all times, which really is the hard part.
I've always consumed a lot of Japanese media so I just continued doing this while adding everything I could to Anki, which is the best tool for language acquisition. Some years later I managed to have actual conversations with people in japan. From what I have gathered this practice is very inefficient but who cares as long as it works out. The most important part, for any skill really, is that you continue learning and using it.
Aside from that, the Genki Books get recommended a lot. I haven't used them but maybe you want to check them out. Personally I just typed "learn japanese" into my favorite search engine and went on from there.