A route that has worked well for many of our travellers looks like this.
Day 1 to 3, Jaipur. Settle in, cover Amber Fort, City Palace, Hawa Mahal and the local markets.
Day 4 to 5, Jodhpur. Drive or take a short flight, explore Mehrangarh Fort and the old city.
Day 6, Jaisalmer or a desert detour, if your itinerary allows extra days.
Day 7 to 9, Udaipur. End the trip at a slower pace, with lake views and a bit of shopping for handicrafts.
Day 10, Fly back to Kolkata from Udaipur airport.
This order works because it moves from the busiest city to the calmest one, so your trip winds down instead of building up to a rush at the end.