Tiers are a way we've implemented to make sure you even out your character growth. You can only level a stat, style, or RP skill up to your tier level and not higher. The only way to raise those items more is to raise your tier.
Below you'll find a listing of the tiers and what is required to advance. In the list, look at the line of your next tier to see the points goals you must reach in each area in order to advance to that tier.
Tier Stats Styles RP Skills 1 0 0 0 2 6 2 7 3 12 6 14 4 20 14 24 5 26 24 34 6 34 34 42