As you said country matters a lot. It can be indonesia, europe, malaysia or any other country.
The gambling license type and google ads certification matters no matter whatever is the country.
Before planning for gambling niche in any country, I would check the geo eligibility, license requirements, advertising verification and landing page compliance with Google Ads for that particular country.
Even a licensed operator can face banning issue with Google Ads if the certification doesn't cover that specific country or gambling category. So no matter whether it is which country, you're going to face difficulties if you don't have any experience with the gambling niche.