It is good to see you are seeing it from the Scanners point of view, and excellent to hear you wish to give scanning a go. When you are new to it, finding only a couple of new Proxies per day is more than enough to deserve recognition. My advice is to find some local IP ranges to scan at first, such as the Class B of your current IP, eg.. 192.168.*.*. These will respond faster and as a result your success rate should be a little better. If all else fails these Proxies will be better for you to use anyway. Find out some friends IP's and scan their ranges aswell.

The biggest problem with suggesting 'good' ranges is that most people have normally scanned them already, so you never find any fresh Proxies. As for ports, the common ones are always worth a shot, 80, 8080, 3128 etc...

Remember, finding 20 fresh Proxies is far better than what 99% of the people in the Proxy scene today will do.