In looking at certificates installed in Web browsers, you may have noticed that (using Internet Explorer terminology, but the situation is the same with any Web browser) the Personal and Other People's lists are empty or nearly empty, while the Intermediate CA and Trusted Root CA lists contain many entries.
This is a fairly typical situation. As an ordinary Web user, you probably don't actually need a certificate of your own - Web businesses such as online banks and shops generally use server-only authentication. As for Other People's, you could install server certificates sent to you by such online businesses, but it's generally unnecessary as these businesses send their certificates in the initial hand-shake of any communication session. It's much more necessary to have CA certificates installed, since these are needed to validate the certificates these businesses send you.
You might sometimes find it useful to install an entity's client certificate, if you communicate with them peer-to-peer rather than client/server.