I am building a HT room(24x17.5x8) it has two walls that are exterior, one is interior, and the other is half and half. The room also has a crawlspace underneath. I plan on putting a thick carpet pad in and plush carpet. The room has no windows and will have an exterior grade door(with a threshold). This room doesn't share any walls with bedrooms, just other living/kitchen areas.

I am not concerned with noise that leaks outside, but I am concerned with others in the house hearing my movies. I planned on going DD and GG on the interior and half-and-half wall. It seems like most people in here are saying that if you aren't going to treat all four walls, the ceiling and the floor then you are wasting money. GG seems to get expensive fast, so I'm not sure my budget can handle doing all that sqft. Is this the truth? Am I better off spending money on drywall clips instead. Is sound flanking going to propose a major problem to me? Is there any cost savings I can get by taking advantage of my exterior facing walls?

Also how do you green glue the floor?

Thanks.

Either treat all walls with DD and GG, or don't both at all. Yes, the truth is that sound flanks around/thru the weakest link. If money is a concern, just use half of the recommended GG for 70% of the benefit.

For the floor put down another layer of plywood with GG between your current floor and the new plywood.

So am I better off using GG all around with no clips or should I invest in the clips and maybe just use GG on the floor?

I assume you say all walls, that includes the ceiling too. I can say that the trusses do not rest on the frame of the room.

I am kind of worried about resonance from the crawl space, as there is quite a lot of volume under there.

I'd just do GG and DD all around. If you want extra isolation then yes you can invest in doing clips on the walls and ceiling. More isolation techniques applied, the better the end results. And yes, I was including ceilings and walls. The cavities you will be stuffing in insolation, so that well take care of the resonance in that area. The crawl space is a bit harder to treat. I've seen people apply insolation to the top of the crawl space, but that can be a big pain to apply.

maybe i can fill the crawlspace with some dirt, after everything is finished. That should take of some it. I guess my next task will be making sure the door I get is solid. Is there any special way that the door should be installed, I am sure it will come pre-hung.