So this method is not an app or a site or tool like that. There are accounts on instagram with similar names like "follow train, gain for gain, 100kfollowers etc." You'd have to follow their page, comment "follow or like" and you'll start getting followers like that. I know someone who increased in followers by 2000 within a week. You'll lose some followers using this method but you'd definitely get a lot more. There are also some accounts that sell followers on ig. You'd have to search for the ones for your country, pay a little token and you'd have the proportional number of followers. Perhaps you can try these methods if they are going to be really worth your precious time.