I also bought all of my copics from Oozak.
Best prices and lightening speed delivery. If you place an order before 3 p.m. Eastern time it ships the same day
I didn't buy any sets either. I have three sites where the designers use Copics most of the time. They always note the Copic colors they used on an image . I chose colors these designers use. My Logic is they own all of the Copic colors and can experiment to find the best blending colors. I will never own all of the colors and the charts on line are not accurate.
They all have tutorials and tips . However Colleen Schaan has a lot of FANTASTIC Copic videos
My favorite Copic sites to check are:
fresh & fun
I am sure there are other sites with great designers these are just my favorites.