What are you installing, and what are you trying to achieve? It really depends on what kind of equipment you are running. - are you running door speakers? What kind of power, how many subs? Etc.....
At minimum, I would go for a layer on the door skin, one layer on the door panel to replace the weather guard. One layer on the quarter panels, and one layer on the rear parcel shelf.
Grab a tape measure, and start doing some math to get an idea of what you need.
I personally use raammat60 -
www.raamaudio.com There are lots of other similar materials out there, but I choose this one.
Some closed and open cell foam could really help as well. The honda plastic interior panels tend to really rattle on themselves.