Pastel plays very well with just about everything out there, and it has a visually distinct homozygous (super) form.

For getting in for a minimum of cost, I'd personally look for a few months until you find "THE" female pastel, once you get an idea of an ideal for a pastel. That'll let you get your foot in the door to raise up a snake for a while to find a good male to pair her with.

Then again, the above could pretty much all be said for spiders as well, with the exception of having a homozygous form.

For me, I just love the yellows in the various combo morphs out there, and one of the best ways to achieve yellows in ball pythons is with the pastel trait.