Gambling 3N usually shows a 7+ running minor with no outside entries.
Responder bids 4C if he doesn't have at least the two majors stopped, then opener can pass if Clubs is his suit or bid 4D if it is Diamonds.
The responses in the database are set for a natural, 25-27 HCP, balanced 3N. If you play Gambling 3N, you need to activate the entries in BidBase for the responses.
Some people play that a Gambling 3N also shows outside stoppers to go with the running minor. That is more like a sure-thing 3N, not gambling, but if you play that way, you will need to change the responses in the database.