I'm a little confused by what your trying to explain but thats cuz I have ADD or something.
The SSRS charts work very much the same as excel pie charts, one thing to try would be to paste a sample dataset in excel and throw a chart on that dataset.
you explain you have 60 different items that go into 6 categories.
The 60 Items would be Groups, and the 6 categories would be the Series.
But as you explain you do not want to show the 60 Different Items.
So you need to add the Category to your Dataset, and then that new Category would be in the Category Group, and the aggregate would be in the values.