tl;dr: Take night school classes for grammar, speech and listening. Use wanikani to “bootstrap” vocab and kanji to accelerate fluency.
I’ve been studying at a relaxed pace for a bit over a year (I could easily pass the JLPT L5, but probably not quite L4). Unlike other posters here, I actually got started by diving into a Japanese 1 night class at a nearby college (two hour class, once a week for 10 weeks), knowing absolutely nothing about the language except “Hai!” I highly recommend this option, if you can find and afford it.
I was quite lucky to get a great instructor. A native speaker of both Japanese (1st) and English (2nd, but no accent!), she would always be happy to diverge for a bit to explain things a step or two past what the textbook explained if she thought it would help students to understand the basics. If you find your teacher doesn’t do this, Google is your friend for finding extra material on a random topic.
Other students in the class varied in level A LOT. Some knew kanji, but not any Japanese. Two knew Korean fluently, but not any Japanese. And some were like me, only knowing western languages. So, with the mix of students, it really helped to observe how others developed ways of handling the grammar, soaked in the vocab, and tried to pronounce the words.
Advice: Learn hiragana and katakana ASAP, and switch to kana versions of your textbook as early as possible. I actually find now that I have difficulty recognizing familiar words when they’re in romaji, whereas I can read them at a reasonable speed in hiragana or katakana (and understand them).
So, I’ve stuck with the class and will be starting my 6th quarter next month. The main reason I came to wanikani is because I now know enough grammar, but am finding I don’t have the vocab to say all the things I want to say, or even to read simple text. This is important for gaining fluency in the language. And, for various reasons, the adult education environment can’t really do much to help you learn kanji or vocab: This is something that requires frequent periods of self-study, at your own pace, and not something you do once a week with a class. So, I will use wanikani to “bootstrap” as I continue studying the grammar in classes.