Here's an article that collects a bunch of the ads I recall from that era.

http://www.collectorsweekly.com/articles/sea-monkeys-and-x-ray-spex/


I think probably the best-known comic book ad is "Hey Skinny", the Charles Atlas bodybuilding ad. And a variation of it, "The Incident that Made A Man out of Mac". Where some musclebound guy on the beach kicks sand in a skinny guy's face, and then he takes the mail-order musclebuilding course, comes back to the beach and kicks the musclebound guy's ass. And his girlfriend comes back to him saying "Ohh Mac! You're real man after all!"