Woolfolk, Boring and Kaye pit Superman against a dragon in issue 86 (Jan. 54).
The dragon emerges from an iceberg, in which it has been floating around, in suspended animation. Coincidentally, Lois and Clark are doing a story on people who claim to be descendants of the Knights of the Round Table, and carry on those customs.
So we wind up with Superman alongside knights in armor riding into battle with a dragon. Simple, but the art is nice.
Mr. Mxyztplk gets his orange and purple suit in this story, by Plastino.
This is also a fairly simple tale, as Mr. Mxyztplk changes the articles in the Daily Planet to be about him. he challenges Superman to a competition to see who can do more, and Superman tries to use this to trick the imp into saying his name backwards. Superman winds up having to get everyone to laugh at Mxyztplk, using feathers to induce it. His pride wounded, Mr. Mxyztplk returns to his dimension on his own.