You can buy your food on board Indigo Airlines. There is no complimentary food but you can surely buy it on the flight on payment. People who pre-book meals at the time of booking or later (only up to 24 hours before the flight time) are served food on-board without needing to pay on the flight. So, if you haven’t pre booked, there are no issues; you can still buy it in the flight whenever you wish to have something. I think this is a better option, rest everyone has their own preference.