A near colorless diamond in the G to J range looks bright and white in a yellow setting, because the warm metal masks the faint tint that platinum or white gold would reveal. Colorless D to F stones are lovely too, but the jump to the top grades is harder to see against gold of this color, so it buys less here than it would in a white metal.
Put what you save on color into cut, which drives sparkle more than any other grade, or into a little more size. A stone a little under 1.5 carats costs noticeably less than one that reaches the mark and looks the same once it is set. Pears and marquises, where color tends to collect at the points, are especially comfortable in yellow.
Karat is the share of pure gold. 14K is 58.3 percent gold, which makes it harder and more resistant to scratches, a sensible choice for prongs and fine detail that take daily knocks. 18K is 75 percent gold, with a deeper, more buttery color and a softer feel, so it shows small marks sooner. If color richness matters most, lean toward 18K; if the ring will lead a busy life, 14K is the practical pick.
Almost any style works. A plain solitaire band with a round center is the most traditional look, and yellow gold solitaire settings show how little the design needs. A yellow gold cathedral setting, with arches lifting the stone, adds height and lets more of the warm metal show. Elongated stones such as oval and pear feel fresh against yellow, and a hidden halo adds a flash of white sparkle beneath the center; see yellow gold hidden halo settings for that look.
Rare Carat resizes rings free for the first year, so if the fit is off or your finger changes, the band can be adjusted at no cost; the resizing policy explains how it works.
Pick the band while you pick the setting, because the head decides how close the two can sit. A cathedral lifts the center and leaves room for a straight band underneath, while a low solitaire head may need a curved or notched band to sit flush. A plain yellow gold band keeps the pair traditional, and a diamond band adds sparkle along the finger. Since yellow gold carries no plating, both rings keep the same warm tone side by side.