You might want to lookup Jainism too
Some people believe that Siddhartha was influenced by Jain monks.
But Jainism in itself is a wonderful study. Unfortunately not much is written about it in English. Mostly everything is written in Gujarati (Indian language)
But Vardhaman Mahavir was the one who came up with Ahimsa (non violence). Atleast thats what many Indian historians believe.
But Jainism didn't spread much outside India. Buddhism did. Buddhism is a very small minority now in India though. Ironically there are more Buddhists in SriLanka or Tibet or Japan than in India.