For a bracelet you wear daily, 14K usually wins. It is 58.3 percent pure gold, and the other metals in the alloy make it harder and more scratch resistant. 18K is 75 percent gold, with a richer, warmer color, but it is softer and marks more easily when it meets a hard surface.
That does not rule 18K out. If the bracelet is for evenings or you are careful with it, the deeper tone is worth having. A useful rule: the more often it will touch a keyboard or a table, the more sense 14K makes.
Hammered gold hides it best. Its small dimples break up the surface, so the fine scratches a wrist collects blend in. A brushed or satin finish, with fine parallel lines and a soft sheen, also disguises light marks and can be refinished later. High polish is mirror bright and the most classic look, but it shows every scratch soonest.
If the bracelet will sit beside a keyboard all week, choose hammered or brushed; if it is for evenings, high polish gives the most shine.
Yellow gold is generous to diamonds. It hides a slightly warmer stone well, so a near colorless line in the G to J range looks bright against it, and you can put more of your budget toward cut, which drives sparkle.
If you are deciding between a plain gold piece and one with diamonds, think about how it will be worn. A plain link is the easiest to stack and the hardest to damage. A diamond piece in yellow gold adds light without losing the warmth that made you want gold in the first place.
Start with one strong piece, a bold link or an open gold cuff, and build around it with finer chains. Varying textures, polished next to twisted or hammered, keeps the stack interesting without adding clutter.
Mixing metals works when it looks intentional. One white piece among several yellow ones can read as a mistake; two or three spread through the stack read as a choice. Compare white gold bracelets if you want a contrasting piece, and carry the warm tone up to your neckline with yellow gold necklaces.