The official Wanikani recommedation is to start grammar BY wanikani level 10 NOT AT level 10. So many people make that mistake.
I recommend you start as soon as you can! I waited until level 10 and was very frustrated by how some textbooks lack of kanji, which made it harder for me personally. Doing grammar, vocab, and kanji at the same time helps level your learning.
There is no one fits all, but here’s the resources I’ve used: Genki 1 (currently working through Genki 2) really helped me learn a lot of grammar and practice. I sued the textbook problems and the workbook. I mostly used the workbook as a review to get some SRS system going.
I also used BunPro a little. It’s really helpful, but I often don’t have time or access to a computer to use BunPro often (and I like learning kanji so I always start with WK when I do have time/access to a computer 
)
I also bother people who speak Japanese to practice with me 
Usually it’s my poor fiance 
Here’s a thread with a bunch of Japanese resources you can look through