I usually check the graph on
https://dicesites.com/graphs under
Daily profit to see how these guys are doing, but the casinos listed there are limited. Most sites has to be calculated manually, based on the statistics that they post on the site and we will not know if these stats are being manipulated.
A gambling site like
https://www.freebitco.in/ has a lot of stats, so you can work out some of the profits based on their 5% house edge. In this case, you have to take the faucet into account too, because it is an daily expense.