I’m not Indian, but I’ve a few Indian friends and have attended a few Indian weddings as well. From what I’ve seen, there’s no “traditional” gift - most of the gifts I’ve seen are something which would be useful for the couple or their house, eg a dinner set, clothes, maybe even a gadget or appliance. But this really depends on the couple - some younger couples these days may explicitly say no to any physical gifts (because they may just end up becoming clutter) and would prefer accepting cash or gift cards instead. So if you’re close to your friend, I’d say ask them upfront what sort of gift they would prefer or if there’s any type of gift they wouldn’t want - and that should help you narrow down. Beware that they may say not to worry about bringing a gift and just your presense would be a gift (I’ve heard this dialog a few times…), but regardless, you shouldn’t back down and insist that you will gift them something irrespective of what they say, so this should make them back down if they’re being stubborn.

As someone else said, a Polish gift might be a good idea - doesn’t have to be a “useful” thing, but something symbolic to remember you would be nice.