When starting to read, your vocabulary and kanji knowledge won’t be the limiting factor. You need to know grammar for that. Think about it: you see a bunch of unknown words in a text, but if you recognize the particles between them and the inflections, and see “oh, this looks like a verb in the volitional form”, “oh, this is an adjective in the past form”. It’s easy to look up new words and kanji. jisho.org makes it trivial (and if you read shounen manga everything will have furigana anyway). Recognizing how the words relate to each other, now that’s the hard part. Learn grammar if you want to read, learn lots and lots of grammar. If you reach around N3 level, you’ll start being comfortable reading simple manga.
The vocab here has only one role: to reinforce the kanji you learn. It’s not sorted by frequency or anything, nor usefulness. There’s many WK words that I have never encountered in the wild. That said, they are helpful to teach kanji readings. You need to use a separate vocab resource, maybe a version of the 6k deck from iKnow.
Just doing WaniKani is insufficient for learning Japanese. WaniKani will just teach you to recognize kanji and words. You need to learn grammar, practice listening and speaking, and learn different vocab outside of WaniKani too. I used iknow.jp for that myself, other people use Anki or Memrise, there’s also kitsun.io which is a nice alternative.
That said, you don’t have to do everything at once if you don’t want to, it depends on your goals. There’s people here who do only WaniKani until level 60 and only then start learning grammar, for example. If you’re fine putting off your Japanese learning by a year or two, that’s also something you decide. Alternatively, if you don’t want to read, but rather only speak the language, then you don’t really need to learn kanji. Luckily in the digital age, you can skip learning to write kanji by hand. Traditionally that’s the biggest time sink for learning the language, repetitively filling notebooks with the same kanji over and over again. With WaniKani that’s a thing of the past, at least. At the very least, try to progress with grammar alongside WaniKani, that’d be my advice. Grammar is absolutely necessary for learning the language either way, so you may as well get started with it.
There’s always some discussion on resources here on the forums, I suggest you look at here to begin with: