I have scripts that follow 50 to 100 per day or you can use humming bird. The problem with following people is that most won't follow you back and that inflates the number of people you're following versus who follows you. That's a red flag for the bots. The best way, really, is to have people follow you naturally because they like you, trust you and enjoy your tweets. I have one account that's growing by 20-30 follows a day just doing that. But even if you get up to 100,000 followers, it's absolutely no guarantee that they will buy anything. Twitter users aren't into buying stuff. They really enjoy shooting the breeze, hashtag gossip and exchanging news links. That's about it. If you post affiliate links on your tweets, then there is no shortage of dumb ass voluntary Twitter police to report you as a spammer. They resent the notion that you might be making a few bucks so they cut you off. If you're a good blogger, you may get some level of traffic using tweet bait. Twitter has never been good for making money.