Gambling is an addiction, and Facebook have no mechanisms in place for users to block all gambling ads.

Yes, you can choose to hide all ads from a specific advertiser, however this task can often be both daunting and unmanageable. Despite not having any "interests" listed in Facebook, my Facebook news feed is bombarded with sponsored ads for gambling sites (slots, casinos, bingo etc).

Facebook will allow you to reduce the number of ads for "Alcohol", "Parenting", "Pets" and "Social issues, elections or politics" yet there is no "Gambling" category.

Facebook need to take some responsibility for the categories of adverts that they allow. Under 18's won't see these ads by default, but those with addictions should have the option to hide them as well. Simply adding the web address of BeGambleAware.org to these ads is not enough. Seeing one of these ads is enough to act as a trigger. 

Facebook - add "Gambling" to the (very short) list of Ad Topics that people can choose to receive fewer ads from.