What kind of proxy should I get?

I'm very new to the whole idea of proxies, all I really know is that I need them for anything blackhat. Basically I'll be using between 30-50 accounts in TweetAttack. Should I buy the proxies they reccomend or go for something differant in case I need them for something else? How many is too many accounts on one proxy?

max 3 per account

Squidproxies ftw