There's nothing certain about who follows back the most as that depends on several facts like the quality of account, kind of niche you're into, amount of posts you have, amount of followers you have, number of people you're following, attractiveness of your profile picture, activity performed by your account on the user's account, the number of likes you've on your most recent pictures, kind of engagement you generate overall and I could keep going on and on...
So, the best way is to ensure maximum follow backs is that your account looks top notch and follows people who're interested in your niche.