I started with Jamie Sams & David Carson's Medicine Cards and Sacred Path Cards. I 'd still recommend them for self development and insight.
The White Eagle Medicine Wheel cards are good also, with a different focus and levels to work with.
Take a look on
www.aeclectic.net They have reviews and scans of decks which is great to help you decide. You can browse by theme, so you don't have to know any names to start.