Creating gallery with taxonomy images plugin?

My code uses a taxonomy category image plugin to display images for categories. It also displays subcategories of the main category in the parent category page (category.php). I want to display only one level of subcategories in the page, for example:

hardware (parent category)

• monitor (first level subcategory of harware)

  • samsung (second level subcategory)

    • lcd (third level subcategory )

When the user clicks on the hardware link, they should see only the monitor subcategory link. Clicking on monitor, they should see the samsung category link, and when they click on samsung, lcd should display.

How I should change my code to achieve this?

My code:

<?php
$cat_id = get_query_var('cat');
$catlist = get_categories('hide_empty=0&child_of=' . $cat_id);
echo "<ul>";

foreach($catlist as $categories_item)
{
echo '<h1><a href="' . get_category_link( $categories_item->term_id ) . '" title="' . sprintf( __( "View all products in %s" ), $categories_item->name ) . '" ' . '>' . $categories_item->name.'</a> </h1> ';

echo '<div class="categoryoverview clearfix">';
    $terms = apply_filters( 'taxonomy-images-get-terms', '' );
    if ( ! empty( $terms ) ) {

      foreach( (array) $terms as $term ) {
        if($term->term_id == $categories_item->term_id) {
           print '<a href="' . esc_url( get_term_link( $term, $term->taxonomy ) ) . '">' . wp_get_attachment_image( $term->image_id, 'thumbnail' );
           echo '</a>';
        }
    }
    echo '<p>'. $categories_item->description; echo '</p>';
}
echo '</div>';
}
echo "</ul>";
?>