Getting traffic is always the main problem of a website. Unfortunately, there is no magic solution.
I do not think paid advertising is a valid method. In my humble opinion, it's a waste of money.
SEO is the royal method for getting traffic in the gambling field. The other methods give very questionable results.
Focus on a particular niche and try to write quality articles centered on long tail keywords. This is the best solution in the long run.
" Money won is twice as sweet as money earned"
Eddie Felson in the movie The Color of Money