Hello Xetish,

The LegendItemTemplate could be modified to add a tooltip for each item in the legend. Here is a code snippet for the same:
<ig:XamPieChart.LegendItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <ContentPresenter Content="{Binding}" ContentTemplate="{Binding Series.LegendItemBadgeTemplate}"/>
                        <TextBlock Text="{Binding Item.Label}" ToolTip="{Binding Item.Spending}"/>                           
                        </StackPanel>
                    </DataTemplate>

                </ig:XamPieChart.LegendItemTemplate>
I have also attached a sample project regarding the same. If you have any questions or concerns feel free to let me know.