Virtually all the online gambling industry is run by casino affiliates who are promoting the big and small branded casinos. Scroll down to the bottom of the first page of any casino website, and you'll find the link for affiliates who wish to sign yup to thier affiliate program. The casino will provide all the marketing tools. For your part, you'll set up a website and try to bring traffic to the online casino you're promoting. It sounds easy, but there's a lot of competition and work needed.