My first attempt. Adding films as I go along, no preplanning here.

RULES:
There must be 31 films
6 countries
Midnight (USA)
Infinity Pool (Canada) 
Whip and the Body (Italy) 
Human Animals (Spain) 
Tender Dracula (France) 
Lair of the White Worm (Britain)
8 decades
Blood of the Vampire (50s)
Whip and the Body (60s) 
The Manitou (70s) 
Midnight (80s) 
Nightbreed (90s) 
Beyond Re-Animator  (00s)
Infinity Pool (2020s) 
2 post apocalyptic or natural disaster related films
Human Animals
She (1984)
1 film with Robert Englund
Freddy’s Revenge
1 something is underground film
X The Unknown
3 Satan/Devil centered films
Midnight
Omen 3 The Final Conflict
Brotherhood of Satan
1 Amicus film.
The Skull
The worst Dracula film (by Letterboxd rating) that you haven't seen and can access.
Dracula 3000
1 LGBTQ+ connected film
Freddy’s Revenge
5 Films from De Palma, Wes Craven, Ken Russell, Hitchcock and/or Moorehead & Benson.
Altered States (Russell)
Serpent and the Rainbow (Craven)
Hills Have Eyes 2 (Craven)
Lair of the White Worm (Russell)
Frenzy (Hitchcock)
2 Peter Cushing films
The Skull
Tender Dracula
1 film based on a work of or invoking the name Bram Stoker
Bram Stokers Burial of the Rats
1 film based on a Clive Barker story
Nightbreed
1 film that was released the year that you turned 10
Lair of the White Worm (1988)
1 Mario Bava film.
Whip and the Body
1 film with an 'x' in the title
X The Unknown
And 1 Tobe Hooper Film (There must ALWAYS be a Hooper film)
Toolbox Murders (2004)