Scott, I know your funds are "budgeted", so may I suggest "Welcome Back to the House of Mystery?" It is a good primer for DC BA horror, as it reprinted some of the best tales from HoM. It was printed in the 90's, so you won't have to shell out too much for it, and might even be able to find it at your LCS.
Also, I know you love EC, so I'd like to suggest a couple titles from the "Copper Age": "Twisted Tales" and "Tales of Terror." Still very affordable. These are some of the best quality books in "recent" memory, and are very reminescent of EC in that they pushed the horror envelope.
Great advice! I'd also add Bronze Mags such as Creepy, Eerie, Vampirella (Warren) and Skywald Mags: Nightmare, Psycho and Scream.
There are a number of Modern Age Horror books out there too, (why not make it an all ages thing?). Titles such as:
Toe Tags - DC
The Lurkers - IDW Publishing
30 Days of Night - IDW Publishing
Remains - IDW Publishing
Silent Hill - IDW Publishing
All good reads and I am aware of the "limited" budget statement, but these are just suggestions to try if you come across them. Aw who am I kidding, make some more money and buy them all!
BTW: Welcome to the Boards!