I dunno if this helps, but I went from 4級 (I guess equivalent to the current N5) to N3 in about two years. The biggest jump for me by far was kanji, which got in my way of learning vocab (which got in my way of learning grammar, which got in my way of learning reading, etc). I barely passed N3 using Genki I+II and the So-Matome series, and didn't feel confident moving on to N2.
I took a few years off of studying, and when I came back last year, I was totally rusty. So I picked up the Remembering the Kanji books, did that for a few months, then jumped into Kanji in Context. Because of that, I learned how to sight-read kanji a LOT faster, which made everything else click into place much easier. I know that not everyone benefits from Remembering the Kanji, but definitely give it (and the Kanji Koohii website) a look if you haven't already. I really wish that I had picked up RTK+Kanji in Context much earlier, as I feel like that would have helped me pass N3 much more confidently in about the same time (or maybe even less) than the So-Matome books. I believe WaniKani uses a similar mnemonic memorization system, though I have never used it.
I still haven't taken N2 (hooray for this panini) but after taking a bunch of practice tests, I feel really confident that I can pass it, and am already aiming for N1. This is after about a year and a half of study (though to be fair, I got in a LOT more studying this time around due to not being able to go outdoors).
As everyone else has said above though, YMMV. I did at least pass N3 using only the So-Matome and Genki books, so it's not like it's impossible. Good luck!!
