To be honest it might be a bit of a futile effort to report frauds here, because depending on the amount of shills they have and the popularity of the site - it can go overlooked for quite some time. You are better off trying to determine the country where the site is hosted or trying to find where the parties who benefit are located, then report your concerns directly to the police force of that country. You should definitely alert people via the scam accusation section here, but such scams can continue to run for a long time so it's worth dropping your scam accusation into places like trustadvisor and other review sites to warn people away from the fraudulent activity you see. Looking at it from the other angle, make sure you really are sure the evidence you've collected is valid and you're not simply trying to get revenge because of losing.