All flights have baggage restrictions. Be sure to familiarize yourself with the restrictions for your airline. Its always good to know the cost of including an extra 23kg bag for your class of travel. You can compare this to the cost and risk of shipping and make a more informed decision. That said, it also helps to carry an empty bag that you can load up while shopping in India. You can also buy cheap suitcases in Dwlhi. Chances are that they will be cheaper here than the USA or Europe.
A lot of my guests join a tour group to travel around India.
If you are joining a group to travel around India, it’s always good to arrive a few days earlier. This gives you time to adjust to the time zone and gives time to shop without getting fleeced. Remember everywhere the tour takes you will be a tourist destination and you cannot hide the fact that you are a tourist, so shopping in Delhi before you tour arrives is a good idea.
In Delhi you will find almost everything that you will find during your tour. Having said that, each state does have some unique items but I doubt that you will see them as a part of a sightseeing tour.
It’s a good idea to ship things back at the start of the tour and not to worry about shopping during the tour. You can pickup smaller items which you can take back in your bag.
If you are at the end of the tour then you can wait till the tour ends to shop and then ship the excess baggage home. I help a lot of my guests ship things back home. We’ve shipped clothes to carpets to the US , Canada and Australia.