Hey Anmol, I might be writting a detailed guide to Sri-Lanka soon here. However have already written a very detailed itinerary for Sri Lanka on my Blog which has day by day itinerary of Sri-Lanka along with all necessary details like flights, visa, accomodation, things to do etc.
Feel free to have a look and let me know in case you have any further questions :) https://travelascetic.com/exploring-tear-drop-island-sri-lanka-part-1/