Measuring all the relative costs and doing it “most efficiently” is hard. Here’s what I did and the things I kept in mind.
Not all kingdoms are the same “difficulty” to get to 5 stars. The number of troops dramatically affects what you have to do. For example, I finished Bright Kingdom last and had to do some traitstone farming, but somehow in Khaziel I’ve still got 5 or 6 troops still at level 1. I recommend doing the “easy” kingdoms with more troops first.
What I did sounded like what you’re doing. I’d sort troops by base rarity and from most common to most rare I did this order:
- Level to 10.
- Do any 1st traits that use only minors/majors I seem to be drowning in.
- Level to 15.
For most kingdoms, this was enough (along with the troops I’d leveled/traited for other game modes. From there it was more art than science. I’d check the Kingdom screen to see how many points I needed. I’d calculate that in levels/traits. Then I’d go pick out the ones I wanted to level or trait to reach that goal.
I managed my souls about like you, but I suggest a bigger buffer. I would accumulate up to 40k souls before attempting this, and only spend down to 30k. Why?
We get 2 new troops/week, and I like to level those. It tends to cost a bit more than 10k. Raids/Invasions also tend to make me need to get a few levels. So 20k felt like it put me at risk of running out. Secondary bonus: last night I only had 2 kingdoms left, and I spent 35k souls maxing them just to get it over with. Now I’m dangerously low on souls, but I accomplished my goal! The bigger your buffer, the more you can do in “one shot”.