Hi there,
I did just exactly what you're planning on doing a few years back, and I've got to say it was a great experience. So many bizarre films, most were awful, but fun awful and some were great films that I'm so glad I've seen and will be favourites with me until I die.
Advice, well the first thing you should get if you don't already have it is the 3 DVD set of "Video Nasties: The Definitive Guide DVD". Trailers and small reviews of all the 72 nasties along with the greatest documentary you'll see on the subject.
As for buying them, I think that ebay would probably be the best bet these days.
I used a few reference sites to decide which versions to buy and which to avoid. These were
DVD Buyer's Video Nasty Guide
and
Plutonium Shores: Video Nasties - Index of Titles Reviewed
Edit : Forgot the Melon Farmers. Also essential reading.
http://www.melonfarmers.co.uk/nasties.htm
My reviews can be found here
https://www.avforums.com/threads/my-...views.1554183/
It is still incomplete, because there is one title that cannot be bought (even now) on legitimate DVD and that is "The Werewolf and the Yeti".
Quite a lot are now available on blu-ray. Those are the versions to buy obviously, but as for the DVDs, I'd go with the versions I've listed in my thread. They are the best of the bunch. Definately avoid Vipco.
You're in for a thrill ride. Enjoy.