Hehe just wanted to share these two really great sites for self-revising Kanji 漢字.
Have to owe it to iKnow! for bringing me to N2 in terms of vocab.
^ no referrals, I've got lifetime iKnow! premium since years ago and kanji garden is free (for now?).
As for grammar... I watched https://youtu.be/nhP_VZtAuro about three to two weeks before the JLPT test.
Not sure how helpful these are.
I'll still recommend reading a lot of Japanese though! Just like how I can read so much more Chinese words now after more than a month of reading three Chinese light novels!!
Also, don't forget to watch anime. Or drama. Although I'm not N1 so this can't be much of a proof, but being an anime fan helped me get full score for listening from N4 to N2 (I didn't take N5)! In total I got 151/180... for N2
So, self-study is definitely possible!! (LIES, I WENT TO A JAPANESE LANGUAGE SCHOOL FOR A YEAR AND A HALF BEFORE I GOT N4 though I was supposed to take N3 and chickened out last minute)
If you can't pay for iKnow!, perhaps try using AnkiSRS and download the Japanese core decks. Flashcard style~
Sorry for any bad grammar not really, please just correct me and lemme learn 谢谢 :')