Would you be willing to answer a few brief questions about PlayStation Forums?
I believe the first ever dlc that I bought was the party pack for Burnout Paradise.
Even that I am not 100% sure if it actually was or not. It was a long time ago.
Probably The Ballad of Gay Tony & The Lost and the Damned.
My first DLC, it's been awhile, I'd say COD4's map pack, maybe a car pack for Burnout Paradise, I think.