I currently started using the filedropper widget as well.
Could you perhaps include some more information about the error?
I got it to work with only the entity, name and relation to context set. It is important to place the widget in the right dataview (with the right source).
You can set the maximum size and amount in the settings.
Also you have to check if your filetype is allowed. You can set this with mimes:
For example, i could not upload a PDF there until i added application/pdf.
Hope i can help you with your issue!