Lots of good advice here. I would recommend that you consult a book on color (there are several excellent ones available on using color in quilts.) Don't just buy what you like. Think outside the box and try to get fabrics from at least the principal color groups (yellows, blues, greens, reds, etc.) You may not have much representation in colors like red-orange or blue-purple at first, but grounding yourself in the basics of the color wheel will help you create vibrant quilts. As others have recommended, don't overlook neutrals like taupe, beige, gray, etc. I never seem to have whites and creams when I need them. I'm not sure if I use them up or if I don't buy them in the first place because they aren't the things that attract me in the fabric shops.
Happy quilting!