Redirect to Theme Customizer after Theme Activation

Drop this code on your functions.php to redirect to customize page after theme activation.

function reflex_theme_activation() {	
	if (is_admin() && isset($_GET['activated']) && 'themes.php' == $GLOBALS['pagenow']) {
		wp_redirect(admin_url('customize.php'));
		exit;
	}
}
add_action( 'after_setup_theme', 'reflex_theme_activation' );