2. You must have good self-control, it is one of the keys to be successful in gambling.
3. You mustn't get loans, you will be trapped in debt at the end.
4. After you can win in a gambling game, you are better to stop (break for a while). Don't be greedy to push your luck!
5. Don't expect much to win in gambling, most of them are luck-based. Think rationally!
6. Don't spend all your time gambling, have enough time for family, friends, and society.
7. Etc
IMO point #2 covers all the other points already and probably cover all the other suggestions which is not yet mentioned. Once you have good self-control then everything will be good as you can control your money, time, feeling, greed, etc.
Frankly speaking, I do not really like your words "keys to be successful in gambling" as it can be something subjective. The word success may mean difference from one to another especially it is related to gambling. I still believe that most people thinks that success in gambling is when they win big.