I started reading them when Mort was the newest one. I quickly acquired the first three, and bought each new one as soon as it came out. He was putting out two books a year for a while there, and it was always a thrill to see a new one on the shelf. I too recommend reading them in publication order.
Wyrd Sisters is one of my all time favourites, and my well worn copy is the one I chose to get signed by the man himself when he came to Brisbane many years ago.
The Discworld has been part of my life for so long that I sometimes forget there are people in the world that have never read any of them. OP is in for a treat.
The titles are: