It depends on the parents and grandparents, etc. If they are subpar then it will take multiple generations of breeding the better of the offspring. But if you start out with good fish then it won't take as long.
I would start with color first - find what you are looking for, color wise, and get the colors strong and stable, after a couple generations bring in another fish with the best fins that are as close to the colors you want.. then breed a baby from them with the best fins back to the parent with the color you want. Then breed the best finned of those, etc.
To make things easier on you, try to get siblings from the breeder, it will help create the color you want quicker.
What color and fin type are you wanting?