6th Singularity Camelot: Roayl Castle free quest is the best AP & time saving location to farm Medal of Great Knight. You'll get about 3-4x Medal of Great Knight by spending 210AP.
Rashoumon event (Ibaraki Douji event)
Murder at the Kogetsukan
Inheritance of Glory
Hero's Proof (Proof of Hero)
Caster Piece
Miss Loveless
Fate Grand Order Farming Items
Sub-Singularity III: Shimousanokuni
Lamp of Demon Sealing
Personal Lesson
Ereshkigal
Arthur Pendragon(Prototype)
Gorgon
Black Holy Grail (The Black Grail)