Examples
Tier I. Doctrine of God, Salvation (Grace Alone, Faith Alone, Christ Alone), Trinity,
Tier II. Baptism (Pedo vs Credo), Spiritual Gifts,
Tier III. Church Government, when to meet, where to meet, Eschatology,
Tier I are Non-Negotiables. The most important Doctrines of the Church
Tier II are Not essential to the Christian Faith. Christian’s hold varying views of the Church, Baptism Operations of the Spirit etc.
Tier III. Not really worth dividing over. There are various views that are tertiary in nature