Best Proxy Services for captcha solving software?

Hi guys, I'm looking for a good service that provides clean proxies that work well with a captcha solving software. As you know there is captcha like Solvemedia that increase difficulty after a few requests and decrease it after a few time. For example, I have calculated that I need at least 100 proxies for work well and smoothly (for the first tests), also I need to contain costs really well in this particular task of the all project.
Another question is in your experience Shared Proxies are over abused from other users and I risk that even rotating them I get back the most difficult captcha? Private Proxies can work well?
Any help is appreciated.
Thanks