// Get an instance of the WC_Order object (same as before)
$order = wc_get_order( $order_id );

$order_id  = $order->get_id(); // Get the order ID
$parent_id = $order->get_parent_id(); // Get the parent order ID (for subscriptions…)

$user_id   = $order->get_user_id(); // Get the costumer ID
$user      = $order->get_user(); // Get the WP_User object

$order_status  = $order->get_status(); // Get the order status (see the conditional method has_status() below)
$currency      = $order->get_currency(); // Get the currency used  
$payment_method = $order->get_payment_method(); // Get the payment method ID
$payment_title = $order->get_payment_method_title(); // Get the payment method title
$date_created  = $order->get_date_created(); // Get date created (WC_DateTime object)
$date_modified = $order->get_date_modified(); // Get date modified (WC_DateTime object)

$billing_country = $order->get_billing_country(); // Customer billing country

// ... and so on ...