That depends on whether you want favor with giants, or more currants. Do whatever works for you.
Personally, I do some of both. Some skills I want to speed up, so I donate my extras. Sometimes I just want to make space in my bags so I sell extra stuff.
*shrug*
It depends on which skill you have. If you want drink skills for instance the cherries will be needed, if you want to make seasoned beans for trees you will need the vapor. You can store some of each until you figure it out or try auctioning.