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sorry but there is no free advertising in this community unless this is for cause for a good deeds and to help those who badly needed.
But what you are asking is for business meaning you are here to make profit so admit that you also need to spend money for advertising.
hire managers here in forum and they knew what to do for your company.
but if you have no budget for this , then best you do it yourself by promoting your site each day every 24 hours of bumping your ANN thread.
Well, I must agree with you... there are ways to advertise a service without any costs, but that means you will have to rely on yourself, and maybe some close people who will offer to work for your casinos without any money!
But... take a look at OP's profile, two posts from June and one from September! Instead to spend some time here, talking with people, maybe he could even find some people interested to work for some little salary at the beginning, or for free, but when the site grows to give them something... but there's nothing from him, maybe he have a wish to do something, but I just don't see it!