I bought an N3 sample exam book and found the grammar questions way too hard. Even looking for answers online was difficult. I could get half of the grammar questions right based on 'this sounds right' but I chickened out and decided to go for the much easier N4. At least get a pass first before I get a possible fail.
That being said, there were a lot of N4 grammar things that I did not and still do not know. My grammar knowledge is practically zero being a self-taught student of the language. I learn Japanese from reading manga, playing games, and watching movies and jdoramas. I know lots of useless in real life words like 初陣 (first battle), 帰還 (return to base) or 召喚 (summon) which will never come up in exams.
There is a part of me that feels like just doing mock exams will not level up my Japanese as a whole or make me understand movies more but there is one thing I realised when taking the JLPT; that its not an exam of filed with trick questions (although there are plenty), its more an exam to confirm the general level of one's Japanese. Though in my case, my vocabulary is a lot better than my grammar.
We only get one JLPT exam a year in December so I got 8 months to start going through the JLPT N3 books I got in Japan during the last trip. I'm feeling very lazy because I have plenty of games to play and mangas to read. In the end, I'm going to be doing the N3 for the sense of achievement and a piece of paper that says my Japanese is at a certain level. In the end, the road to being fluent in Japanese is a never ending one. Will I ever get there, I don't know.
On a side note, anyone have anymore 2017 jdoramas to recommend? The only ones on my to watch list now are Shimokita Die Hard, ByPlayers and Ishitsubute.