Metals fall into two primary groups in a decorative sense, those being the gold and brass family on the one hand and silver and steel on the other. Of the two, gold is easier to wear if significantly more expensive. Gold does not tarnish and so is virtually maintenance free, requiring only a periodic cleaning to remove the inevitable dirt build-up. Most wedding rings are gold, simplifying one part of the metals problem, and gold is a better complement to white for evening and to navy jackets - particularly blazers with brass or gold buttons - at any time.
The expense of gold can be ameliorated with a steel and gold wristwatch like the one in the photo. Gold and silver watches and watch bands are suited only for day wear (the old custom said gentlemen do not wear wristwatches in the evening anyway) but they help coordinate the day's other metals. Equally appropriate is a collection of four watches, two of them gold and two of them silver. One of each pair should be mated with a black and the other a brown alligator band that will match the day's shoes (this stuff gets complex). Now that cell phones have effectively killed the watch as anything other than jewelry however, having multiple watches really begins to seem like overkill unless watch collecting becomes an aim in itself. But I digress.
Most usefully, the steel and gold watch lends itself to silver cufflinks that can be a better complement than gold to a gray jacket. Silver of course is shorthand for a variety of substances including white gold and the best of those is platinum which is more durable than white gold and lacks gold's impurities (nickle was used to color the stuff in the past and though unlikely to do damage should ideally not be worn next to the skin).
Belt buckles, being visible, should also relate to the day's other metals. The best way to achieve this is with interchangeable straps and buckles but the equally appropriate alternative is the four belt rotation consisting of brown with silver, brown with gold, black with silver and black with gold. But by now you get the picture.