Go back into the Reading settings and set the posts per page setting to the desired amount for all your pages (not what you want for home, i'll get to that).
Once you've done that, add this to your theme's functions.php file.
function home_posts_per_page( $query ) {
if( $query->is_home )
$query->set( 'posts_per_page' , 1 );
return $query;
}
add_filter( 'pre_get_posts' , 'home_posts_per_page' );
Reference of other threads with similar questions, using similar code.
http://wordpress.org/support/topic/347269
http://wordpress.org/support/topic/393462
http://wordpress.org/support/topic/367338
NOTE: Please ensure code is pasted correctly, after an opening PHP tag, eg. <?php, most likely easiest if you place the code after the first line with the opening tag.