Definitely go with a pastel for ball pythons. Unless you plan on getting into breeding for morphs. I'm not personally a fan of spiders, but you can get gorgeous little bumblebees out of them.
As for other snakes, you can get a Western hognose, a young normal phase rtb, or just about any kingsnake, milksnake, or New World rat snake under the sun. Mexican black kings are beautiful lil guys.
That being said, I'd still go with a little more, and maybe you'd be able to pick up a few supplies for a good deal while you're there.