check with your gynae ask your gynae to scan for you. mostly gynae recommended is 2 years later. but some mummies wound took longer to heal it really depend on individual. I had a friend who gave birth 18 months apart twins pregnancy she mention it was so much more painful than first 2 pregnancy
My OB-GYN said it is ok to conceive after 18 months. There is no ideal gap honestly as there are so many factors to consider. Listen to your body.