Bad idea. 1) Quantity does not translate to quality 2) No way to measure ROI 3) Most of "bulk sellers" require your twitter's account credentials, bad , bad, bad! 4) I kept the best for the end, indeed Twitter does not allow it.
As Engine said build your followers slowly. when in return they follow you, use direct thanks message with a dedicated comment about their profile background, web, tweets,comments, etc. make it personal so they will feel enticed to look in depth to your own profile. Be useful and not marketer to the teeth.
Henry, thanks a lot. I an very happy into the forum. The only thing with Tweetdeck is that it is not in the cloud, itīs a desktop software. Plus I cannot access to Linkedin groups as I can from Hootsuite.