The better gambling sites to consider are the ones running a signature campaigns here. Haven't heard gamblers complain about them at any point in time.
Not all the time, there are gambling sites that aren't cryptocurrency-related, that's why they often didn't advertise in signature and bitcointalk, but it doesn't necessarily mean that these sites are bad.
Sometimes, what makes a gambling site good, is when they chose to advertise in bitcointalk and they get tons of players which generates profits for the site to improve and develop their features.
Another advantage is when people provide their feedback, so the site will already know what to improve.
I think most sites that are popular in crypto space advertise in bitcointalk.
Bitcointalk has a big audience and we have real people here who are knowledgeable enough to determine if the site is legit or not, and they also provide some help from their feedback. I remember in the past, there are only few gambling sites advertising in the forum either from the site slot or signature campaign, but now they are growing in numbers, in fact, majority of the active signature campaign now are from gambling sites.