Well that's some task.
Well from FTD label you can start trying to get this ones:
-Elvis in Person (Classic Albums series, not to confuse with the Legacy edition of it). Which is the original '69 L.P. plus the August 22 '69 Dinner Show.
-Elvis At The International. Which is the August 23 '69 Midnight Show.
-Live in Las Vegas. Which is the Aug 26 '69 Dinner show.
-All Shook Up. Which is the Aug 26 '69 Midnight show
-Polk Salad Annie. Different dates from February 1970.
-One Night In Vegas. August 10, 1970 Opening Show.
-The Wonder Of You. August 13, 1970 Dinner show.
From the Mainstream Label you can start out going for this ones:
-On Stage [Legacy Edition] This is like the definitive vegas Album on the mainstream label to me. It has the two classic vegas albums: On Stage from Feb 1970, and In Person from Aug 1969. Plus some bonus tracks.
-Elvis: Live in las Vegas Box set. Here is the full Aug 24 '69 Dinner Show, and the full Aug 11 '70 Dinner Show. Plus you will get the full 1956 performance, all the live masters from vegas Feb 1970, and Feb 1972, and a bunch of rarities from 1974.
-The Special Edition 3cd set of That's The Way It Is, which has the original album, the Aug 12 1970 Midnight show, some extra live perfromances from the same season, and rehearsals.
-Now the import version of the Viva Las Vegas soundtrack (not the soundtrack of the '64 film but to a documental about Elvis in Vegas), contains a bonus Cd wit hthe full Aug 21, '69 Midnight Show.
There is much more both in FTD and in the mainstream label, plus the bootleg world, but those are the basics to me. If you are going from zero, the Live in Las Vegas box set is a great way to start.
Hope this was usefull to you. Sure other members will provide with much more indeep lists.