Need help with is_user_logged_in

This is the basic code:

<?php
if ( is_user_logged_in() ) {
    echo 'Welcome, registered user!';
} else {
    echo 'Welcome, visitor!';
}
?>

PHP:

But when user is logged in I want the out put like this: Welcome, FIRST NAME OF THE PERSON, if first name field is empty then the USERNAME of the logged in user.