I am in a bit of the same dilemma. I know I want the Sketch. After spending hours reading the threads and checking the recommended blogs, tutorials, and online places like Flourishes for advice on colors; I thought I had my list made.
Then I found a list someone posted giving the Copic matches for Stampin' Up colors. Being a former demo I have all the paper and this is what I use when I make cards. So...I thought maybe I should go with the matches for the colors I use most often. After watching a tutorial on YouTube with someone who uses only the very lightest in a color group ( those that end with 000's for example) and a very dark shade to do all her blending, I thought maybe that system would work for me and I could get lots of colors I like and still keep it to a total of 30 markers.
I've got my list ready but I haven't bitten the bullet yet and ordered anywhere. I've checked out Carpediem.com and know how much it would cost to place the order there. It's a huge jump for me to take but after playing with two or three of these markers I really like them. I will get my courage up soon I think!