You need to retweet other people frequently (daily if you can), and interact as much as possible with other users content. It's all about those retweets and stars, nothing to do with follower count. The followers trickle in as you get the exposure from retweets, faves, @replies and hastags, so don't focus on that number.
There is a real odd culture of giving to get on Twitter, if you retweet and interact with the right people, chances are they will retweet you. Any notification avalanches I have gotten, have been from bigger accounts (35,000+ followers) retweeting me after I interacted with them via @replies, or they saw my content on someone else's account as a retweet. I have 795 followers, and my top tweet has 237 stars and 130 retweets. While it's not a lot, I can guarantee most of those aren't from my own followers.
Make sure to check out their profile too, if their tweets have stars and re-tweets, you know they have an audience, so interacting with them might benefit you. As shitty as if sounds, people who tweet a lot, but no one interacts with their content, are lesser in terms of exposure. Even if they re-tweet you, it won't reach anyone, so it's nice, but long term it's not really beneficial.
Just assumed every single account doesn't know you exist until you interact with them... because that's how it is.
It's also proven if you put "Please RT", you'll get more retweets. Not sure how you feel about that though, I avoid it.
So.
Forget the numbers.
Focus on:
Interacting with people as much as possible (@replies, hashtags, faves and re-tweets)
Re-tweeting and faving relevant content (remember, you can un-retweet later to clear up your profile a little)
Tweet the same content link more than once, but change the title or the text in the tweet (tweets have an average life of 24 minutes)
If anyone interacts with your content, they @reply you, make sure to star it, so they know you acknowledge their tweet.
But 100% the most important thing, interact with as many people as possible as much as possible.