For the typical mid-range independent jeweler, merchandise-buying patterns have changed significantly in the last five years. Here are the top seven trends:Moving upscale and relying on designer lines to lure shoppers. "We can't get the margins we once did on diamonds," says Lew Hill, co-owner of Van Scoy Jewelers in Wyomissing, Pa. Hill found a solution in designer bridal lines, which "increased the sophistication" of his bridal jewelry offerings. As a result, profits from engagement sales now come from the mountings. Van Alexander, owner of Alexander's Jewelers in Texarkana, Texas, decided in the late 's to "go designer." "My goal four years ago was to get the No. 1 brand in every [jewelry] category," he recalls. One big advantage of having top designer brands is that they attract a wide range of customers. "The same Yurman piece can appeal to 85-year-old women and 18-year-old women,"