As a champion, you can get a focus pool of 3 at level 6 by taking multiclass archetype feats. One possible path:
- Level 1: Devotion Spells champion class feature, getting one focus point.
- Level 2: Monk Dedication feat.
- Level 4: Basic Kata feat, granting the Ki Rush or Ki Strike feats, which grant a second focus point.
- Level 6: Litany Against Wrath feat, granting a third focus point.
The text of Ki Rush and Ki Strike says they grant a focus pool with one point, but the Focus Points from Multiple Sources sidebar makes it clear that this will increase the size of an existing focus pool.
You can swap out the monk dedication for any other multiclass archetype to a class which has a level 1 or 2 feat which grants a focus point.