You can see everything it affects
here, but the main things good luck does, (both daily and buffs from food etc.) is:
- Increases your chances to find a ladder/shaft. Useful when you're trying to get to the bottom of the mines or for a deep dive in the skull cavern for iridium.
- Increases your chances to find a treasure room in the

cavern and geodes in any mine.
- Better chance to get a treasure chest while fishing, and the chance of that chest being golden, if you have the fishing mastery.
- Better items from panning
I think that's everything important