My niche is very broad actually, so there's a lot of content I can choose from. Also, an account that's very niche focused doesn't always work out. I have this Game of Thrones account at just above 200k and the only time it gets me solid growth is when a season is live, other than that, I get like 300~ followers daily by just posting a few times a day.
Also, by high quality posts I'm talking about pictures that will get your account to explore, only then you'll be able to expose yourself to millions(not exaggerating). I reach 3 million accounts in a month, and get 8 million views in a month