Over the Summer I picked up a couple of toy dolls on the cheap at yard sales.
You could do this project with Dollar Store toys, but I paid half that for both my dolls by shopping at yard sales.
I had 40¢ in my pocket so I offered that for this doll and my offer was accepted.
This doll (fashion doll head) was in a 10¢ box:
Then all you basically need is paint, scissors, any accessories, and imagination.
I painted this one, and used my staple-gun and hot glue gun to give her a nasty gash on her face.
Her "teeth" are the tips of toothpicks.
The other doll I cut/plucked her hair with pliers and dyed, and painted. That's pretty much it.
There's a lot more ideas for Creepy Altered Dolls on Pinterest and the Internet, ranging from simple to advanced.