Well this is just my perspective though its more neccesary to grow your twiiter acc not to buy and if you wanted to buy you better gather some intel , and talk in p2p or person to person , where you agree or even bargain  depend on what price or what is the seller want or you want. I just want to leave an advice for you , dont be an instant , do the hard work and surely it pays off. Be wise and be careful there are tons of sellers yes but there are many , millions and even billions of scammer. So be aware and good luck.