There is a great post on the forums that discusses the findings of a mathematical analysis of the Championship Points in Elder Scrolls.
The analysis effectively demonstrates that there are dead zones between CP’s spent at various level that provide no additional benefit to the player.
The key table for the non-mathematician is the one below
The tables show that between various CP’s spent, no additional benefit is obtained as a result. Therefore, the analysis recommends that you spend your CP’s at the values above.
For example, if you 80 CP’s left and wanted to max Blessed (15% maximum), it would be optimal to spend 75 in Blessed (14%) and 5 in a 25% Node (eg. Elfborn) for 2% over 0% in Blessed.