You do not need to start
spamming with your service offer. Just create the topic on a board and see the replies of people and you may be lucky. No need of making different topics for the same offer. Know that your other thread would be deleted.
You can also look for others means to look for casinos and other gambling sites that can accept your offer. You can reach the gambling sites through their customer care or social media handle which their customer care can see your offer and direct you to where you can make such offer.