You should always try to buy, or get given, the most expensive belt possible. It is often seen when your jacket is open, and more so when it is off. It lasts a long time. It should preferrably be the same colour as your shoes; and, if you are very natty, it could be in the same leather as your wrist strap. In principle a narrow belt is flattering if you are not so young; if you are young, a really wide belt can be dashing and avant garde.