I'd say a good place to start is to just get a Toto album with a collection of songs. One of the greatest hits-type compilations would be good. Then, you can delve in to the individual albums. "Toto Live In Amsterdam" is also good. I have to get the DVD now. I think that Lucious does a fantastic job on the latest album "Falling In Between." Also, you can check out some of his Los Lobotomys stuff.
You can also check out his discography on his site and kind of cherry pick a song here, a song there, an album here, an album there.
http://www.stevelukather.net/Discography.aspx
Recently, I put together a little mix CD with some Luke moments. Not necessarily his coolest/rocking-est stuff from a guitarist's perspective, but it was meant to kind of show the range of stuff he's done with stuff that's recognizable and entertaining to your average, everyday pop music listener. Songs include the following:
"Beat It" - Michael Jackson
"Human Nature" - Michael Jackson
"Stand Back" - Stevie Nicks
"Talk to Ya Later" - The Tubes
"She's a Beauty" - The Tubes
"Dirty Laundry" - Don Henley
"What's Going On" - Joe Cocker
"Baby Come to Me" - Patti Austin
"We're In This Love Together" - Al Jarreau
"Gimme The Goods" - Boz Scaggs
"Forever Man" - Eric Clapton
"Turn Your Love Around" - George Benson
"25 or 6 to 4" (1986 version) - Chicago
"I Keep Forgettin'" - Michael McDonald
"I Gotta Try" - Michael McDonald
I can't remember if there are any other ones, but I think that's all.
Happy hunting.