Buying Copics can be a monumental task if you allow it to be. There are over 350 colors . Don't jump in and buy every pretty color you see. They are all pretty
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I think it is important to learn how the markers react by doing solid coloring first. When I started I did only solid coloring with no shading.
Jumping into shading before you know how the markers work on paper is like trying to run before you can walk.
Find an image you want to color. Research just that image in the gallery or on blogs to see what colors others used for it and only buy those colors to begin.
If you start out with too many colors that don't work together you will become discouraged. If you go at this slowly you will acquire a Copic collection of colors that you like and will work well together.