From Creepy #1:
Pg 22-23: (between "Vampires Fly At Dusk" and "Werewolf") 2 page ad for another Warren Publication, "Monster World".
Pg 36: (just before "The Success Story") Capt. Co ads for a "Magnajector", Rodan in 8mm, Revenge of Frankenstein in 8mm, and a replica of a human skull
Pg 43: an ad for a Warren special publication devoted to the film "The Mole People"
Pg 44: (just before "Pursuit of the Vampire") More Captain Co ads. Miniature Germanium Radio, 10' inflatable snake, Phantom of the Opera in both 8mm and 16mm, Miniature Spy Camera, and Venus Fly Traps.
And that's all of them. There isn't a single advertisement anywhere to be seen from an outside source. Compared to modern magazines the early Warren Mags certainly don't seem to be very ad heavy!