Do you think it is a bad thing to do, promoting gambling?
No not really provided that you do it to the right audience
Your audience should be a group of sensible and responsible adults who can make their own decisions of course we are talking about morals and ethics but if we talk about it legally then it would be different since it would mostly depend on your country's rules and regulations. Going back to morals and ethics, I think promoting gambling is not necessarily a bad thing as long as you are not promoting scams fully knowing that what you are promoting is indeed a scam and would put your audience to harm
We won't be able to control who is seeing our ads because the internet is so vast, so in my opinion, it will depend on the regulations of the country where we live. If gambling is not banned in your country, advertising gambling is not considered bad because we only advertise to people in need and we do not force anyone, so it cannot be considered bad. But if it is banned in your country then you will be considered as someone who spreads social evils and you are a bad person.
In addition, one thing we need to keep in mind is that we need to carefully check and evaluate the casinos that we cooperate and promote. We should choose and only cooperate with reputable gambling websites, not just for profit but willing to accept the promotion of scam casinos.