If you ever buy diamond ring pieces to fill your jewelry box, avoid the following mistakes to get the most value for your money.     Selecting a Diamond with Best Color and Clarity Choosing the best clarity and color diamond by paying a premium price is not always a wise thing to do, as attested to by experienced jewelers. The naked eye cannot really tell the distinction between a diamond with extremely top rated color and clarity, and one with ratings just below. The color of the gem is measured upon a scale of D to J, with D being the best. However, a diamond with G color would look just about the same as another with D color unless the two are assessed under 10x magnification. Flawless or FL is the top diamond clarity grade, going down to SI-2, meaning it has some blemishes and marks. Often, jewelers recommend a diamond with VS-1 (very slight inclusions) clarity grade.     Narrow bands are extremely popular these days, mainly because a diamond set on a thinner band looks bigger. It makes for a beautiful diamond ring, though choosing an extremely narrow band would not be wise in terms of durability.