I've grown my personal account enough to now being doing paid Instagram work in my country, and getting free overseas trips (pending on these trips I could have a lot more opportunities coming up)
My biggest things, have a niche and stick very closely to it. The bigger you get, the harder it is to post unrelated content. People follow you to see one thing and if you don't post it, it will hurt your engagement. Also pick something you know about, as people who know your niche will see right through you.
I don't post daily as my content is too hard to produce daily. I try and just post 2/3 times on week days. Always try and post high quality content. Selfies almost always get the best engagement (for me anyways, no I'm not a bikini IG model and show everything to get thirsty boys to like me). I do try to mix up my feed, then post a shot that I know will go well and go a little bit viral to keep me out there and infront of people.
I grew my account using bots and liking. I know in my niche there's a few people bigger than me, a reasonable amount of people around the same size as me (though our niches are slightly different, we fall under the same overall category) and a heap of people trying to make their accounts into something. I tend to target the smaller accounts and like their followers photos. The followers of smaller accounts tend to follow more (in my experience). If they're willing to follow someone with ok content with 50k less followers, they're going to follow the bigger account with good content.
Thats all I can think of off the top of my head, hope it helps!