The Order of The Golden Dawn was and may still be a real sect, it was created in the early 20th century by Aleister Crowley.
English Voice Actors for Asta & Noelle, Dallas Reid & Jill Harris, are actually married in real life.
The four main kingdoms in the story - the Clover, Heart, Diamond and Spade Kingdoms - are all named after the four classes of playing cards; specifically the French cards, which refer to the club as the clover.
Most of the Magic Knights and some citizens have names that correlate with the type/style of magic that they wield and in some rare cases, the name can denote the person's job, such as the town mayor named Mayor.
The anime has script writers who worked on JoJo's Bizarre Adventure and Monster (2004)