Everybody should read more of Buddha's Teachings... the wonderful four Noble Truths. The Middle Path and the Eight-fold Path are the quintessence of Buddha's teachings. Everybody should read the New Testament of Jesus Christ. Everybody should read the Bhagawad Gita. We should methodically incorporate all their teachings in our daily lives.
When an old soul transcends, it is called as 'Arihant'. When it goes back/ comes back as a helper of mankind as spiritual teacher, it is called as the 'Bodhisattva'. After completing a number of teaching assignments, finally as a perfect master the final life is lived. It then goes on to become an Overself, this stage is called as 'Buddhahood'.