OP wants an advise but is not here to direct on what exactly he wants. Meanwhile, I don't think there are gambling sites that are 100% skill rather the skill could be seen as experience. And luck is also part of it.
You literally reiterated what the poster above you wrote. Seriously?
I am looking for a buy-in game competition. Not cards, or casino games. something like COD.
Does anybody have one they can point me to?
Why in the world didn't you mention what COD means in this context? This error led to a variety of answers from different people trying to help you out.