Every time I go to bot something or have a great idea for a bot I find out that the website already has pretty good bot detection. The worst thing is that if a site finds out you've got multiple accounts and you're spamming they can just delete every account with your IP. So, theres always needs for proxies, but they are expensive even if you buy cheaper semi-dedicated ones. I saw there was a thread on here posting some new proxies, but other than relying on random posts on different forums for proxies, what do you do? Just suck it up and buy them? I also still don't understand how there are 'free' ones to scrape.
When I was creating and using bots in the past, I used the most of the time a tool named Proxy Finder Enterprise - there is also Socks Proxy Search from the same author (but I think that the first is better and just enough for any need), and both grabbed thousands of proxies. Then, I used Charon to filter them i.e. check if they're valid and work against the site I was targeting; and everything worked fine. That grabbers are not updated anymore, but I've tested the first recently and I think that it works the same like earlier (and presumably for the second it's the same case). The first two tools I've mentioned above are commercial, so probably you could still find pirated versions of them on the Internet. If you don't want to search for them though, then I can send you all three tools in a single package.