I'm sure I'm going to forget or haven't found some, but off the top of my head Gale will accept:
- The Necromancy of Thay book available from the hidden workshop under the blighted workshop - you'll also need the amethyst to open it from the caves below before Gale can use it. Astarion also wants the book, and you can read it yourself to get the Speak with Dead spell.
- The sword from the paladin in the toll house, which you can get whether or not you side with him over Karlach.
- The iron flask from the chest you can "liberate" after dealing with the Zhentarim trapped in a cave by gnoll. This will have gameplay consequences though minimal in early access.
- The idol of Silvanus in the centre of the druid grove. Stealing before getting the druids to stop their ritual will result in a bloodbath, though it can be stolen once the ritual is aborted by those whose morals permit it without leading to mass murder. Though if you steal it you might want to give it to Mol instead to help encourage youthful enterprise.
- The Staff of Crones from the back room down in Ethel's lair.
- The Selunite amulet from the room behind Dror Ragzlin in the sanctum in the goblin camp.
- The mask available from the back room in the Myconid village in the Underdark, available as a reward for dealing with the duergar slavers for the Myconid King ... I think, though I've generally dealt with Gale's condition if I'm going to before this point, so perhaps am misremembering.
I'm sure there's a more reliable list somewhere else on the internet, or even on these forums!
I generally give him the amulet and either the staff or sword which I don't tend to have other uses for. He only needs two items, in Early Access at least.