There are circumstances where order matters
The example in the OP is the same either way, but the order in which you take the Deity's Domain feat does matter, because it does not explicitly give you a focus pool.
You automatically gain a focus pool of 1 Focus Point the first time you gain an ability that gives you a focus spell.
This means that if Deity's Domain is your first focus spell, then you gain a focus pool from it. However, if it is not your first focus spell, you do not gain any focus points from it.
For instance, if you were a cleric with the Domain Initiate feat, you would have a pool with 1 Focus Point. Let’s say you then took the champion multiclass archetype and the Healing Touch feat. Normally, this feat would give you a focus pool. Since you already have one, it instead increases your existing pool’s capacity by 1.
Most focus spells explicitly grant you a focus pool, therefore the above rule can apply to them, raising your focus pool by 1. Deity's Domain, however, does not explicitly grant you a pool, which means it only grants a pool if it's your first focus spell.
In conclusion, if you are a monk:
- If you take Ki Rush, then multiclass into Champion and take Deity's Domain, you will have one focus point.
- If you multiclass into Champion and take Deity's Domain, then take Ki Rush, you will have two focus points.