Do you have any intention of increasing your Ball Python collection and possibly getting into breeding in the future? If so, I would try and get a female first. At that price range, you could find a Lesser, Mojave, Pastel, Vanilla, and MAYBE even a Super Pastel if you negotiate well enough. I was told if you intend to breed, purchase the female first as it takes longer for them to mature to a healthy breeding weight.
If you do not plan on ever breeding and really just want to get the coolest morph you can for your money, then get a male. You could possibly find a Bumblebee (I've seen them as low as $275), Pastel Lesser, Pastave (Pastel + Mojave), etc. It really just depends on what you like and what you plan on doing in the future with them. This is just from what I've seen shopping online for Ball Pythons.
Good luck and make sure and look online at prices so you don't pay more than you should! Know what you are buying and what the normal value for that particular morph is. Hope you find your perfect snake!