I like to get my grammar studying in in a variety of ways. My #1 favorite way is talking with people through Line, HelloTalk, Twitter, etc. If I see grammar I don’t know, I look it up and write it down for later, more in-depth study. Not only does this introduce me to new grammar, it shows me grammar people are using in conversation and I’ve already got context for it to start with.
Another way is books. Slice of life manga and 小説 are great for this. Fairly everyday grammar, and depending on the novel, you’ll get some more complicated grammar in there as well. Plus this is a great way to work on additional vocab, too.
YouTube comes third. I’m also a huge fan of Nihongo no Mori. I think they’re hilarious and the teachers explain things well, and since it’s explained in Japanese (I’ve only watched N3 and above videos so I’m not sure about the N5/N4 ones), you get familiar with the Japanese context in a way you don’t when learning Japanese in English. I know a lot of people recommended Japanese with Misa but I find her really boring. Her videos are too long and she’s a little…dry and emotionless? I can’t explain it, but I’d recommend reading her blog over watching her videos. I usually have to quit after 4-5 minutes into her videos.
Finally, I use a lot of online resources like Japanese Test 4 You and Maggie Sensei. Tae Kim’s Guide to Japanese is good too, but I don’t love it. I’d also really recommend imabi.net. It’s better than any textbook in my opinion.
Sorry that was so long, but I hope it provided a little insight!