Admitting you have a problem with gambling is half the battle! Your half way home already!
I mean you can see the problems gambling is creating in your life. You see it and it is something that your mind will play around with. Watch it crave and make up all sorts of excuses and logics to convince you to gamble once again. It will create these stories and will make the solution gambling. Your mind is wrong. Nothing bad about that. Perfectly fine to be wrong sometimes. But you see it now... otherwise you would not have posted this.
Seems obvious to state the following, but it is worth mentioning.
Stay away from whatever it is you are trying to quit. If you drink... no bars. If you gamble.. no casinos or race tracks. Do what you can not put yourself into a situation where you will have a temptation.
I think the biggest thing you have to do it is make that big decision to quit gambling one day. The day you just say "Enough is enough!" and you never gamble again.
Does the thought of never gambling again make you uneasy? If so... really look at that... feel it. That is the addiction staring you in the face. Hard to face addiction. Don't want to look at it or feel it. The only way to really get over you addiction is through practice, perseverance and most of all loving yourself. Surround yourself with people that will support you. You can do this! Just gotta go through the hard work of quitting. Good thing in your case is that it is not a physical addiction. This is all just mind games. Quit playing the mind games. Quit and don't look back.
DMT may help you see your gambling problem in a new perspective... and maybe it won't help at all. Don't rely on something external. It is all on you! Many things you have tried have not worked out with the lowest common denominator being you. Sounds like you are on the right track and a good line of thinking right now. Like I said, your halfway home.
Good luck to you!
"In the universe there is an immeasurable, indescribable force which shamans call intent, and absolutely everything that exists in the entire cosmos is attached to intent by a connecting link." ~Carlos Castaneda