I have a few copic markers, not many. But what I suggest is you use copic ciao first. They don't have as many colors as the copic sketch markers but they are also double ended like the sketch. Another thing is the ciao markers are cheaper than the sketch.
When I was searching up information I found this to be the cheapest place to buy them: carpediemstore.com (also just so you know if you add the markers to the cart they are cheaper than what they list. I don't know why they do that).
If anything on the colors it all depends on what you draw. You may just want to buy your own instead of a set that way you get to pick the colors.
[link] <---This artist is a copic marker user and these are her favorite markers. It also gives you an idea of what some of the markers (obviously not all) look like.
Oh and if you are doing outlines or inking make sure you get waterproof ink! Most ink pens are that way now. If your willing to spend the money copic also has copic multiliner pens which are pretty nice to.
In my opinion they are worth buying. They are refillable and one refill bottle can refill a sketch marker up to 10 times or so.
When I started buying copics I just bought 3 or 4 of them that are in the same family (blending) group to see if I would like them. Well now I have around 170. But that was buying them in a period of about 3 years individually.