Here is a guide to look over and possibly use on your generals for their skill trees, these setups are designed to maximize their uses and reduce losses overall for multiple adventures, of course there are some variations depending on your game play as well as numbers of generals you may have and which generals you have, but these designs are for usage in combination with other generals to maximize adventure completion with reduced costs and time within Barracks. Now, also take into consideration your level for some of the skills, if you are already max level, you might look at changing some of the skills from the Experience boosting skills to another skill, however, if/when they increase the level cap again, you might wish you had kept the Experience boosting skills.
I will start out with explaining/displaying the skills themselves and how they effect the generals and what the costs are to gain in the various tiers of the skills for those that do not have any experience with skill trees for the generals or that do not understand the process or the skills themselves.
Here are the different skills available for the generals
For each new tier of skills, requires 5 skills more in the lower tiers
So, for example (to help some understand)
If you put 5 manuscripts into this tier of skills
It will open up the next tier of skills
5 Tomes into that tier and/or Manuscripts in the one below it will open the next tier
5 Tomes into that tier and/or the tier below it and/or manuscripts in the first tier will open the next tier
5 Codex's into that tier and/or Tomes in the previous 2 tiers and/or manuscripts in the first tier will open the last tier
So, for each tier after the first one, requires 5 more "books" to open the next tier, whether it is Manuscripts, Tomes or Codex's is your choice after the first tier, so, it's 5 Manuscripts to open second tier, 10 "books" (Tomes or Manuscripts) total to open 3rd tier, 15 "books"
(Manuscripts or Tomes) total to open 4th tier and so on and so forth.