3 compilations /anthology collections for your stater set (these are multi disc sets that will act as a great intro and must have's even for seasoned reggea lovers)
Peter Tosh-Honorary Citizen
Bob Marley-Songs of Freedom
Lee Perry-Arkology
The liner notes are dope as hell as well...
A must see if you can find it is 'Red X'-documentary of Peter Tosh- greatest reggae artist of all time.
You need some King Tubby for sure
Also check out Lee 'Scratch' Perry. With out King Tubby or Lee Perry West Coast hip-hop wouldn't be what it is today. Their catalog is so deep though, I advise opening a Pandora account and make a few stations of theirs. Dub reggea from the late 60's/70's is the shit though, bout laid back and dope as it gets.
Can't forget Max Romeo
Jimmy Cliff's the harder they come is a classic
Toots and the Maytals is nice, but they're not Rasta's but still they get down.
For contemporary, Jr. Gong (aka Damian Marley) as some select choice cuts