Lee is correct. I wonder, Follow your HEART, if you are thinking of "Don't gamble" and "No gambling"? "Don't gamble" could be used if you are talking to someone, and giving them advice, or could be a command. "No gambling" would be a rule or command, and is much more formal.

"no gambling" is more natural, because "gambling" is a noun. Generally if you use the word "no" before a word to indicate a negative command, the word after will be a noun. Usually the noun form of a verb. "no gamble" is understood, but it is incorrect, because "gamble" is the verb form and verbs are not negated with the word "no."