I second most of the suggestions on climbing gear. Just like getting started in traditional archery, talk to someone at a local shop like REI that sells climbing gear. Explain your exact need and they can be very helpful. Ascenders like the Petzel, Black Diamond, Jumar, etc... can be expensive, but having done single rope ascending in caves and up overhangs, they are worth every penny.
NEVER buy used climbing gear. You do not *know* the history of the item. Carabiners can develop microscopic cracks if mishandled, a dynamic rope is considered done after a climb with a fall. Pretty much every climbing magazine, website, and climber I know agree on this 100%