1. DC Comics Present #26 (1980): Her first appearance ever.
2. The New Teen Titans Vol 1: Her beginnings with the Teen Titans, and explains why The Justice League didn't really help with Trigon.
3. The Terror of Trigon (The New Teen Titans Vol 2, #1-5): This is an extremely Raven-centric story, as well as being one of the greatest Teen Titans stories ever told.