I wouldn't pay for twitter followers. The best way to get them is to trade retweets / mentions with other big name twitter users.
Pay attention to the names that get tagged often in tweets, as they are usually the big players over there. Try it yourself too, but retweet some of their tweets first.
Also use hashtags, these are some of the popular days of the week tags that always trend
#MirrorMonday, #TittyTuesday, #WetWednesday or #AssWednesday, #ThongThursday, #FriskyFriday, #SexySaturday, and #SexySunday or #SinfulSunday
Hope that helps a bit
(Edit) I just realized this was in the mainstream category.. I was thinking adult when replying, however it all still applies other than the hashtags I think.;)