I'd definitely start with Leviticus & Chronicles
See if they're in it to win it....
In seriousness, it'd really depend on their background. If they were Jewish I'd probably recommend they start with Matthew. If they were very modern minded I might start them with Luke-Acts. If they are a particularly passionate person I might start them with Mark. And if they are a deep thinker I might start them with John.
And after they read one of the above, I'd recommend James