Narrow it down by settling three questions: how many prongs, how much detail on the band, and which metal color. Four prongs leave more of the stone on view. Six grip it at more points, which is reassuring if you work with your hands, and they make a round outline look rounder still. A plain band keeps every eye on the center, while a band with fine detail adds interest without competing with it.
Metal color matters more than most people expect. White gold and platinum reveal any warmth in a diamond, while yellow and rose gold soften it, so the metal you settle on can shift which color grade is worth paying for.
With no halo or side stones to share attention, the center diamond is the ring. Spend on cut first, because cut decides sparkle; for a round, aim for Excellent on a GIA report or Ideal on an IGI report. Clarity only has to be eye clean, meaning nothing visible without magnification at a normal distance, and in brilliant shapes VS2 and plenty of SI1 stones get there.
Size is the other lever. Prices climb at round weights, so a diamond weighing 0.90 to 0.99 carats rather than a full carat costs noticeably less and looks no different on the hand. Start in the loose diamond search and filter by shape, cut and weight before you commit to a band.
Every shape can stand alone, and the head of the setting is made to suit it. A round gives the most sparkle and hides small inclusions and a hint of color well. An oval or pear looks bigger than a round of the same weight and makes the finger appear longer, though elongated brilliants can show a bow tie, a dark band across the middle, so watch the video before you buy. Stones with points or corners, such as pear, marquise and princess, need V prongs to guard those edges. If an elongated look appeals, line up a few oval cut diamonds against rounds of similar weight.
Either order works, but it is usually easier to choose the diamond first. The stone decides the budget, the shape and the size of the head, and it is the part you cannot change later without starting over. If you already know the style you want, browse finished looks among solitaire engagement rings for women, then come back here to build it around your own stone.
Every Rare Carat ring setting is covered by a lifetime manufacturing warranty, and resizing costs nothing during the first year, so a band that turns out a little snug is an easy fix.