spend more so earn more

You can't just spend on advertising without studying or making an effective plan, it will just a waste of money. I think you can visit other gambling site list down their promotions and improve it to have an effective promotion and advertise it in the forum to get players. Giveaways or signature campaign that pays in the account of the users in the gambling site could be a good idea too.
Indeed , but what he mentioned as i understand is the willingness and the capacity of the team , their dedication and showing of how they wanted to gain popularity and players , and with that they need to spend in advertising , promotions and even give away so at least they may have good impressions from the legit and gamblers that looking for whom they need to trust.
Advertising certainluy needs to be integrated into a wider startegy. The gambling market is quite packed with sites and it is technically simple to setup a new site and create content is not really expensive, so like in the startups it is all about growing fast and growing cheap. You cannot count on going viral, so you would do best in finding a niche that can be reached by an specific campaign and get a foothold with these clietns.