Be careful with maximum concentration as it may lead you into addiction, gambling should be fun and concentrating too much in the game may make you forget the other things.
In other side, having concentration will not change the result of your gambling so gambling should be made enjoyable.
It can be by communicating with others while gambling (in chat room), listening to music, or some other things.
Too much concentration may also make you too much stressed, so I have to say that too much concentration is something really bad for gambler unless you are playing pvp based game such as poker or skill based game such as sports betting.
The maximum constraint here is that we don't try to do anything other than gamble in our spare time so we won't forget to know when to stop. It will help if we also have strong self-discipline so that nothing will happen to us. Concentration won't change the result but can give us pleasure in playing because we can focus on playing while we don't think or do anything else and stop at the right time. Maybe you can communicate in the chat room while you play gambling but that can also interfere with your concentration playing gambling. So I think the maximum concentration here will vary between gamblers.