Testing? If you wanted a lifetime's supply of Mr. Goodbars, you should have said something. You could have had anything. Money, women,...men? But wouldn't do a deal for the Eyes. What the Hell's the point of that?
Start with It. It's by far the better book. The Stand is good. But I think it's missing something. It has a main villain, but you don't see the effects as much as in other King books. In It, you really want to side with the main characters. The villain is prevalent, and his effects are felt throughout the book. You want to see the enemy get what it deserves.
If I could add some recommendations; the entire The Dark Tower series. It's composed of 7 books (and soon to include an 8th, which takes place in the middle). But truthfully, it encompasses around half of King's works (they all take place within the same Multiverse). King considers it his magnum opus, but you would have to classify it in the fantasy genre rather than the horror genre. That's not to say it doesn't have his style.
As for more simpler recommendations: for rookies into the horror genre, I'd say his earlier works (Carrie, Christine, The Shining, Firestarter, etc.). But I always enjoyed one of his works from the mid 90s: Desperation. There was something about it. It just gave off the right atmosphere to make you...worried, scared, I dunno. You may laugh, but a great book will do that to you.
“Power in the hands of the reformer is no less potentially corrupting than in the hands of the oppressor.”