What are more valuable; proofs or uncirculated, or commemorative?

I am a Viet Nam vet. Took my son to see the traveling wall about 7 years ago. He's in the service and that visit to the wall meant a lot to me. I want to get him the viet nam $1 silver coin. There is also a 3 coin set out there w/the coin I want, the POW $1 (which also means a lot) plus the female service $1. I see $99 to $159. Some say proof, some say uncirculated. I want the coin for my son, but I also don't want to get ripped off. Being a disabled vet on limited income I try to watch how I spend. Any istance would be appreciated. I need to get these ordered and in the mail. I am kind of on a time schedule. Appreciate any and all help!