Best Sources of Exp/Drop Buffs

There's also an exp buff you can obtain from part-time job, but I don't know specifics of it.

You can get 1.3x EXP as a random additional reward after doing Resting or whatever it's called, if not Resting than something very similar.

Unique IA when using the regular Circulators can land on 15% drop rate.

Legendary Potentials on Accessories can have certain percentages (don't remember off the top of my head) for drop rate.

Got the IA the other day, isn't it 13%?

Pots are 10%/15%/20% and align with the normal potential tiers.