Each item can only be donated once, so it's actually a bit difficult to get the rewards that require the most items donated.
All rewards from donating items to the Museum in My Time at Portia3: Small Waste Bin.
5: Magician's Hat.
10: Recovery Machine
20: Colorful Hat.
30: Safety Box.
40: Cushioned Couch and Party Table.
50: Marble Flower Bed.