4th Singularity London: Southwark free quest is the best AP & time-saving location to farm Homunculus Baby. You'll get about 3x Homunculus Baby by spending 190AP. Evil Bone is also dropped.
Here is a list of servants that need Homunculus Baby to perform Ascension and Skill Up.
Note: No Bond CE's here.
5 Star Servants Tier List
Best Servants [★4]
Christmas event [JP 2016 Rerun]
FGO Reroll Tier List
Holy Night Supper
Piece of Year 2030