There’s no reason to buy matching watch/belt/sunglasses sets. They are separate items and don’t need to relate to each other, but perhaps should be the necessary style to,go with whatever look you’re going for.
It’s normal to have a dress watch with a dark leather band and a sports watch with a stainless steel bracelet, just as it’s normal to have dress belts and other belts to be worn with jeans or cords.
Pocket knife is also always a good idea. Isn't there a “daily carry” thread devoted to things like pen knives and such?