There is one true God who reveals himself to the world as the Father, Son, and Holy Spirit, commonly referred to today as the Trinity doctrine (Matthew 28:19).
Each individual must, through faith and obedience, reach out to receive this free gift of salvation when they are mature enough to understand the consequences of their sins (James 2:14-26, Luke 14:25-33) When people repent and are baptized, their sins are forgiven and the Holy Spirit begins to work in their lives (Acts 2:36-41).
The greatest command in the Bible is as Jesus stated in Matthew 22:37-39: to love God with all your heart and mind, and to love your neighbor as yourself.
While salvation is based on grace and not our good works, disciples have a responsibility to live and work for God as laid out in the Bible. This includes helping others to become disciples (Matthew 28:18-19), encouraging one another to love God and stay faithful to Him (Matthew 28:20, Hebrews 3:12-13, Colossians 1:28-29), and serving the poor and needy (James 1:27)