I've found that most of the stock reports don't lend themselves well to creating Pie Charts. To get the best use of Pie Charts you'll likely want to create new Report Definitions with custom SQL.
If you take a look at the report "Agent State Real Time Graph", the definition is built such that it just returns rows with state names (Not Ready, Talking, etc) and counts of agents in those states. The Pie Chart for that report uses the "NumInState" as the Data, and "AgentState" (the name of the state) as the Label.
In the case of any other report built into the system, you'll probably want to use the EnterpriseName field (or SkillGroupName in the case of Peripheral Skill Group Real Time All Fields) as the Label Field. Try out any field that gives numerical values for the Data field. For example, you could use "LoggedOn", and you would then have a pie chart comparing the number of agents logged into each of your selected Skill Groups.
-Jameson
-Jameson