5th Singularity E Pluribus Unum: Des Moines (Surveillance Fortress) free quest is the best AP & time-saving location to farm Claw of Chaos. You'll get about 2x Claw of Chaos by spending 180AP.
7th Singularity Babylonia: Ur (Jaguar Park) free quest is one of the other locations to farm Claw of Chaos. You can also get Seed of Yggdrasil.
2nd Singularity Septem: Germania (The Dark Forest) is the first location you unlock to farm Claw of Chaos, but the item rarely drops.
You can also farm Claw of Chaos at Wednesday Daily Quest: Berserker Traning Ground. For other item drops, check the table below.
Kara no Kyoukai (The Garden of Sinners) event
Kara no Kyoukai Event Rerun
Journey to The West
Kara no Kyoukai (The Garden of sinners) Event (The Garden of Order)
5 Star Servants Tier List: Best Servants [5★]
Best Servants [★4]: 4 Star Tier List
1-3 Star Servants Tier List
Ryougi Shiki (Saber)
Ryougi Shiki (Assassin)
FGO Reroll Tier List
Jeanne d’Arc (Alter)
Holy Night Supper
Black Holy Grail (The Black Grail)