Go to this blog to learn everything there is to know about Copics:
http://ilikemarkers.blogspot.com/
Marianne is absolutely wonderful and will also answer any questions you may have. However, if you start at the beginning of her blog, you probably won't have any questions! I wasn't sure what to buy when I first started (I now have about 90 or so colors), so I went with Sketch and I love them! I started by buying two or three in each color family (blues, greens, browns, yellows, pinks, purples). Buy them with 1 or 2 numbers apart and in the same family (for example, B21, B23, B24). I'm not exactly sure these numbers are available, but it should give you an idea. If the numbers change form 28 to 31, they are probably not compatible. Colors change within the family by the middle number. I can't really explain this well. Read Marianne's blog, she explains it. I buy mine at
www.oozak.com They sell Sketch for $3.80 each and shipping is free if you spend $50. Service is great!
Good luck! I'm sure you'll love them once you try them! You'll never change to anything else!
Janet