Post as much as you like, share stories, reply to comments, message people who’ve messaged you, and engage with friends and accounts in your niche. All good, all encouraged.
Go steady on bulk following, unfollowing and rapid-fire liking, since that’s the same activity we’re running and the totals add up on Instagram’s side.
Two things worth avoiding entirely: cold DMs to people who haven’t messaged you first, and copy-paste comments. Instagram polices both heavily no matter who’s doing them.