Hi Mariana,
The property Spacing helps you to control the space between the columns in a chart.
The property SpacingBetweenSeries helps you to control the space between the series only when they are in SideBySide display and also in 3D mode.
Please try the attached sample which helps you to control the space between the series when they are in SideBySide and 3D mode.
I will create a bug report on this regard and let you know at the earliest once it is fixed for non 3D mode.
Thank you for your continued interest in Syncfusion products.
Regards,
Jaya
ColumnChartSample.zip