As Gandhi, win a cultural victory with 3 or fewer cities in your empire.
Do puppet cities count towards this limit or not?
I'd assume they probably are (since you do get culture from Puppet cities), but it would be nice to know.
I can confirm this. I had three cities as India and later conquered and puppetted two cities thinking I'd be good, but did not get the achievement after a cultural victory.
I got it in another game where I got a culture victory with India with only my capital.