Add pagination to WP_Query (posts by tags)

How do i add pagination to this.. i tried it my self but nothing works for me.. the pagination isn’t showing..

<?php
    $args=array(
      'tag' => gtags_get_group_tags(),
      'caller_get_posts'=>1,
      'posts_per_page'=>3

    );
    $my_query = new WP_Query($args);
    if( $my_query->have_posts() ) {

      while ($my_query->have_posts()) : $my_query->the_post(); ?>

<!--- my post list --->

<?php
 endwhile;
$big = 999999999; // need an unlikely integer

echo paginate_links( array(
        'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
        'format' => '?paged=%#%',
        'current' => max( 1, get_query_var('paged') ),
        'total' => $wp_query->max_num_pages
) );
 } //if ($my_query)
 wp_reset_query();
?>