Mandalas can be as simple or complex as desired. Is all based for me on the mood. By starting with simple shapes allows me to finish quick. Sometimes the simple drawings get a makeover, by adding more shapes and patterns everywhere possible. You can even keep adding more shapes and patterns to a finished Mandala but make sure you have a big sheet of paper!.
I usually start with pencil and when done, I trace my design with a permanent fine marker. I try to use the permanent marker when I have a design ready for more details in the shapes or new shapes. You need to start with pencil and when you feel comfortable you can continue with the permanent marker. You can also start with the marker, is all up to you. Once completed it can be left alone if desired but why not color it in.