I highly recommend starting grammar as soon as possible. Otherwise Wanikani feels pointless, because where then do you apply what you’ve learned?
I get motivated myself when I see the progress I’ve made. Wanikani is a program intended for learning kanji; I’m assuming you’re studying kanji to be able to read literature in Japanese.
Even a bit every day can go a long way. Don’t become fixated on how much you can learn in a short amount of time. Small things build up. In September last year, I started formally learning grammar. Each day, I would do one section in Genki 2, whether that be taking notes on a new grammar concept or doing an exercise.
I could not imagine reading even a book for children in Japanese back then, but now I’ve finished one picture book and two manga, and I can really see the progress I’ve made in speed and understanding.
You may have already seen this farmous guide linked around the forum: My Journey of 368 days (+ The Ultimate Guide for WK 📖 ) - #2 by jprspereira
Try reading the section “Building your own schedule.” Basically, three small sessions of WK per day is a lot more efficient and less demotivating than one huge one.
My own schedule is a loose version of this:
Lessons and reviews at 5pm
A smaller review session at 9pm comprising of the newly learned items
A longer session at 7am the next day. This is when I will do the bulk of the reviews.
For a better and more thorough explanation of SRS intervals and how you can use WK efficiently, read the guide 
Good luck!