My road to N3 level went like this:
WaniKani (around 8 days per level after level 3 when the level up times are normal)
Genki I and II, along with their respective audio and workbooks (N5 and N4 grammar)
Tobira (N3+ Grammar)
I started wanikani around the same time as I started the grammar books. I think Genki I and II in all were around 24 lessons, and Tobira was like 15 lessons. So going with around 1 lesson a week and you would have plenty of time to use other resources, or go a bit slower.
Now I am just waiting for my Wanikani level to go up as I learn more kanji, so that when my school studies lessen a bit I can continue to the N2 book, New Authentic Japanese, along with a reading speed helper book called Rapid Reading Japanese. And after that I plan on using Shinkanzen Master N1 series to wrap up my JLPT studies.
There are tons of resources out there, even free ones like Tae Kim’s grammar which I think sets you from 0 to around N4 level. Also sites for grammar like bunpro, and bunpo. Good luck finding your best method!