If you are looking for cheapest way to travel from Delhi to Dawki , then you can go for a train ride . The nearest train station from Dawki is Guwahati Station. There are more than 10 trains that stop GHY Station ( Northeast express, New Delhi to GHY express etc.) . From GHY station to Dawki the distance is around 180 KM. You can take a bus ride there , It will take around 5 hours .
I hope this will be useful for you 😊.