What's marvelous about gridnhouse cinema is that it's just so vast - there's so much idiosyncratic and wonderful stuff (and, admittedly, unredeemable trash) that I'm not sure a definitive canon will ever be put together. Many grindhouse historians would say that the work of trash auteur Al Adamson (represented above in BLOOD OF GHASTLY HORROR, ANGEL'S WILD WOMEN, and NURSE SHERRI, and available in copious doses on Jaman) is a great place to start, but there are thousands of crazy films floating around out there.
Additionally, many would argue that the spirit of grindhouse filmmaking died when the original grindhouses (regional theatres down South, fleapit houses on 42nd Street in New York) closed, and yet I can't help but think that the spirit of grindhouse filmmaking is alive and well amongst the DV auteurs churning out low-rent zombie videos for local film fests, and in many of the unreleased horrors given a place to roost here on Jaman.
After completing the trailer grid I honestly thought that I'd be happy to roll the dice and take in a random double feature picked from any of the movies above. As for where to start, I'd say just dive on in. Any revulsion, disappointment, hilarity and surprise you feel is par for the course.