Well...as I've only had two reptiles as pets, I'll tell you what -isn't- a good first reptile: Green Iguanas

My BP is the first reptile I've had as an adult (meaning I'm an adult, not the BP)--and he's super easy. The set-up and supplies were a hefty first-time expense, but once I had an ideal setup husbandry (and safety)-wise, keeping him has been a dream so far. Clean up the soiled substrate, wash out the tub, fresh water, feed him once a week--and that's it. He's pretty low-maintenance.

Though from what I hear, geckos are good first-time pets I've never had one, though.