My custom template page not loading content inside it?

you have to use the WP Loop to get page content. Try this

<?php
/* Template Name: home */
get_header();
?>
<div id="theme-main-banner" class="banner-three gradient-banner-three">
   <?php while(have_posts()): the_post(); ?>
       <?php the_content(); ?>
   <?php endwhile; ?>
</div>
<?php get_footer(); ?>  

UPDATE

The issue was that front-page.php was already present in the theme. So as per the Template Hierarchy it has higher priority, renaming/removing it solved the issue