spend a whole day at the purple mountain to visit all the attractions.

One day is not enough to cover all the sites on the mountain. I recommend you to visit the most famous three, Xiaoling Mausoleum of Ming Dynasty, Dr. Sun Yat-sen's Mausoleum and Linggu Temple. There is no much difference to start from any of them as all have metro station nearby and there are sightseeing buses shuttling between.

If you still have time left, go to the mountain top by cable or on foot to have an open view of the city.