Searching for a Legitimate and Reputable Online Gambling Site
To paraphrase Abraham Lincoln's sage advice -- recounted in a popular online meme: "Don't believe everything you read on the Internet." This goes for the many, many thousands of Internet gambling websites where you are depositing your bets. If it is 100% legitimate, you have rights and recourse:
(1) there will be a licensing agency you can turn to in the event of a dispute;
(2) you have assurance that the site is not a criminal enterprise and has the resources to pay debts;
(3) you can sue them, if necessary.
Conversely, an unlicensed site could be a scam or fraud: an attempt to get your bank or personal identifying information, or a way to get money from you that you'll never see again. Even if not actively criminal, in the event of a dispute between you and then, you will likely have no recourse, since illegal transactions are not enforced by the courts (see our article on enforcing gambling debts).
Finding a reputable domestic online gambling website
It's surprisingly easy. First, start with the basic proposition that in the United States, all gambling is illegal unless specifically authorized by a state. As of November 2018, only four U.S. states authorize online gambling: DE, NV, NJ, and PA (though PA does not have any active online gambling sites). Any state allowing gambling will have a government agency which regulates and enforces the gambling laws. In New Jersey, for example, the Division of Gaming Enforcement or NJDGE lists the authorized gambling operators or providers. If you are looking at a website which claims it is licensed by or based in New Jersey, check the DGE's website to see if it is on the authorized list of providers.
What about sites that don't indicate where they operate or by whom they are licensed? That's equally simple: assume they are not legitimate sites, since there is no reason a legitimate operator would not have this information somewhere on their website. If you want to do a little more "due diligence," to give the site the benefit of the doubt (i.e., assume that the omission of the jurisdiction licensing them is just an oversight), "Google" the site or otherwise do an online search on the search engine of your choice. If you turn up a location where it is supposedly based or licensed, go to that jurisdiction's gambling regulator's website and see if they are licensed. Again, any legitimate site is licensed somewhere; and if you can't locate any place in which they claim to be or should be licensed, that means they are unlicensed--and so, not legitimate.
Finding a legitimate foreign online gambling sites
The same rules apply to foreign sites: either find evidence that it is licensed and regulated or don't trust it. If you can't locate any jurisdiction (i.e., any country) licensing them, assume the operation is unlicensed and so illegitimate. If the gambling operation’s website does state where or by whom it is licensed, take one more step and log on to the nation's gambling regulator's website and confirm.
For example, for a relatively tiny (221 sq. miles; 83,000 people) "self-governing British Crown Dependency," the Isle of Man licenses a surprisingly large number of online gaming providers: 38 operators/licensees as of November 2018, providing 73 gambling websites (some "full service," some focusing on a single or only a few games), including such big names as PokerStars and William Hill. (Favorable tax rules and relatively easy-to-comply with regulations account for the Isle of Man's popularity as a licensing site.) The Isle of Man Gambling Supervision Commission has a webpage listing all their licensees as well as those with suspended licenses.
Keep in mind, though, that when an overseas licensed provider is legitimate and reputable and that you have rights and recourse, taking legal action overseas or in a foreign country is never as easy as taking legal action domestically. In that regard, you are always better protected when gambling with a licensed U.S. online provider than a foreign licensed one.
General online and business opportunity advice
The oft-used mantra “if it sounds too good to be true, it probably is" also applies to online gambling sites offering unbelievably good promotions, bonuses, or alleged returns (i.e., an incredibly high claimed percentage of winners). Just because the deal sounds great, doesn’t mean it is. The virtual world can be very seductive--but also very treacherous, and online scams abound. Reputable websites and opportunities only offer you what the "market" generally does--that is, what you can broadly expect from other legitimate opportunities. It's the fraudulent sites, businesses, and opportunities that promise you the moon, because it's easy to make inflated promises when you have no intention of keeping them.