I have a site that hits the sweet spot for that demographic but my user base is 90% in the U.S.
It seems like it is okay to do for now but is still a grey area. Here's a good article that goes into detail about this:
While the legality of online gaming itself is still an open question as a result of conflicting court decisions and stalled legislation, the legal issues relating to advertising online gambling services are even more obscure. One of the reasons is that the power of the government to regulate advertising of a particular product or service is not coextensive with its ability to regulate or ban the same product or service.
The concept of Internet gaming advertising raises a host of legal issues that are dependant on a number of factors, including the medium chosen for the promotion and the potential applicability of various state and/or federal laws. The courts will employ the same legal analysis used to evaluate traditional gambling advertising regulations, but under a relatively new paradigm that is based on the underlying premise that the government’s power to prohibit or regulate particular conduct does not necessarily include the power to prohibit or regulate speech about that conduct.57 The traditional justifications for imposing restrictions on gambling advertising may well be lacking in the context of online gambling promotion. Virtual casinos do not generate increased prostitution or drug activity, and have not been historically infiltrated by organized crime. The inability to effectively geographically limit the target audience for online gambling advertising may also impair the government’s ability to constitutionally restrict advertising about online gaming services to areas where it is considered a legal activity. Thus far, the United States government has not specifically legislated in the area of Internet gambling, let alone the advertising of such services. While the various states have touched on this subject, or have enacted legislation which appears to regulate or prohibit such promotions, the validity of any such laws as applied to virtual casinos is questionable.
If speaking about Google Adwords, it supports responsible gambling advertising with the condition that it meets the Gambling ads standards. https://support.google.com/adspolicy/answer/6008942?visit_id=636842806628138245-446114262&rd=1