Best way to get user id for get_users function?

Your code doesn’t work because you’re using $bloguser instead of $user.

And there’s no point in calling get_userdata() since get_users() already returns user objects:

foreach ($blogusers as $user) {
    echo '<tr>';
        echo '<td>'. $user->first_name .'</td>';
        echo '<td>'. $user->last_name .'</td>';
        echo '<td>'. $user->user_login .'</td>';
        echo '<td>'. $user->user_email .'</td>';
    echo '</tr>';
}