My trip was for only 10days in vietnam excluding traveling time from India.
I booked return ticket from delhi to ho chi minh which i got for 20k with air asia in which i was not allowed to to take check in baggage i was with only hand baggage and that was all okay. And I bet you can get return ticket of air asia for 16k also. We booked 15 days prior our journey.
Then I applied for approval letter for 17$ then in 48 hrs i received through email my approval letter thn I paid 25$ on visa on arrival for stamp duty.
Then after getting visa i headed towards domestic airport and took a flight to hanoi from where my trip would start. I booked vietjet for rs 3000 approx.