if you take 1 dimension,1 expression it will show clear data or if you want to write 6 expression you can go for straight table or pivot is the best option
Pie Chart is not made to show more than 1 expression.However, the message you are getting might be not because of this. Most Probably ,Expression values might not be large enough to be displayed reason being number of dimension values are too high.Try to restrict Number of dimensions values.
