Changed my mind and decided to make a list this year. I'm sure this will change quite a bit as I'm actually going through, both the order and what I'm watching, but this will serve as a good roadmap in general. There's no unifying theme, but as you can see there's a strong Italian horror/gialli bias to the list with a lot of Bava, Fulci, and Argento. I'm going through their films chronologically and then throwing in random other films to break them up as I go along, finally ending on a nice gothic haunted house film that I have heard compared favorably to The Haunting, which means I will probably love it.
All of these are first time viewings, but I'm sure some rewatches will sneak in here or there as I go along. Since this isn't locked in at all, if you have any suggestions on either movies to add/replace or changes to the order feel free to let me know!
1) The Whip and the Body (Mario Bava, 1963)
2) The Last Man on Earth (Ubaldo Ragona & Sidney Salkow, 1964)
3) Kill, Baby, Kill (Mario Bava, 1966)
4) Spider Baby (Jack Hill, 1967)
5) Five Dolls for an August Moon (Mario Bava, 1970)
6) The Wailing (Na Hong-jin, 2016)
7) Hatchet for a Honeymoon (Mario Bava, 1970)
8) Jigoku (Nobuo Nakagawa, 1960)
9) Death Walks on High Heels (Luciano Ercoli, 1971)
10) A Bay of Blood (Mario Bava, 1971)
11) The Cat O'Nine Tails (Dario Argento, 1971)
12) Don't Torture a Duckling (Lucio Fulci, 1972)
13) White Zombie (Victor Gordon Halperin, 1932)
14) What Have You Done to Solange? (Massimo Dallamano, 1972)
15) Baron Blood (Mario Bava, 1972)
16) Haxan (Benjamin Christensen, 1922)
17) Lisa and the Devil (Mario Bava, 1973)
18) Torso (Sergio Martino, 1973)
19) Deep Red (Dario Argento, 1975)
20) Shivers (David Cronenberg, 1975)
21) The Driller Killer (Abel Ferrera, 1979)
22) City of the Living Dead (Lucio Fulci, 1980)
23) Cannibal Holocaust (Ruggero Deodato, 1980)
24) Bloody Birthday (Ed Hunt, 1981)
25) The Beyond (Lucio Fulci, 1981)
26) Sleepaway Camp (Robert Hiltzick, 1983)
27) Demons (Lamberto Bava, 1985)
28) Hush (Mike Flanagan, 2016)
29) Pulse (Kiyoshi Kurosawa, 2001)
30) Opera (Dario Argento, 1987)
31) The Innocents (Jack Clayton, 1961)