Order of advancement
 

I noticed that there is some sort of order in advancing rage spirit abilities. Is there some diagram of this?

For example, I want to advance Glot's Armour, what would I need to pick in order to get more opportunities to advance it?

When the spirit achieves new level all available skills a placed in the one list, and then 2 of them are presented for upgrade (the posibility for all skills are equal).

On the other hand, when your Spirit achieves appropriate level for new skill, it is given forcibly, instead of one already available. If you don't accept it, next time it eill be added to the list of available ones, and presented on the basis, mentioned in the first paragraph.

So basically it's random, and the randomness is diminished only when you skipped a new ability?

almost random, but it even rises with the new level, as there appear more variants in the skill list with equel posibility.

So if I skip a skill there will be a higher chance of selecting what I want because of the fewer selection pool at the next leveling?

Only a little, still there is a chance you will have it on next level up however it will be basic skill so one choice more only, if u take skill it can have several types of upgrade ( rest,cost,power etc)