well it varies day by day because we don't know how many user win and losses, still in the long run, gambling site will always win but you will need to find one with good trust and proven fair else its mostly scam
Ya make sure we check the background of the gambling site we wan to invest.This is because some site got hacked when the they already have a huge amount of margin from investor.Maybe the real hacker or maybe the owner of the site opening a loophole and claiming the site was hacked.