It is really hard to find attorneys that practice this type of law. I would suggest googling first amendment attorneys because they are the ones who usually deal with escorts, gambling, and everything controversial. Lawrence G Walters has a great reputation in this area.
What you will learn soon is that there is no way, and no legitimate attorney that will give you a green light to run such a project. You will notice that most operators of such sites incorporate in more privacy friendly jurisdictions such as Panama. This still brings with it complications of being probed for money laundering. The US government does not like these private juridictions and will treat you as a criminal, if they ever find out you are attached to such a project. Their concern would be you are in Panama due to tax evasion.
Further, thanks to the Bush administration, US citizens cannot take advantage of offshore gambling sites. Many still do, and risk getting into trouble.
My advise, build it in Panama, keep it in Panama, never connect it to the USA. Never bring the cash to the USA. Keep it all in the Panamanian corporation. Makes it rough if you cannot enjoy your money, but that's the safest way I would approach this.