HOW DO RULER SKILLS ALTER YOUR COUNTRY MODIFIERS ?

The main component of my mod is Step System.
For every level of your ruler's skill your country gains specific country modifier.

Currently, there are 6 steps:
• At 0-1 ruler skill (by that I mean ADM, DIP and MIL of the ruler) your country will suffer the worst modifier (lvl 1)
  
• At ruler skill = 2 your country will have slightly better, but still negative modifier (lvl 2)
  
• At ruler skill = 3 your country won't have any modifier (lvl 3)
  
• At ruler skill = 4 your country will have small positive modifier (lvl 4)
  
• At ruler skill = 5 your country will have significant positive modifier (lvl 5)
  
• At ruler skill = 6 your country will keep lvl 5 bonuses and you will be able to choose specialization.

There are 4 types of specialization per each ruler skill:
for ADM:
- Great Administrator (bonus to taxes and reduces stability cost)
- Great Builder (reduced building price)
- Religious Leader (missionary strenght, toleration of your faith and bonus to papal relations)
- Administrative Thinker (reduced administrative tech cost)
for DIP
- Grand Admiral (increased naval morale and reduced ship building time)
- Great Merchant (increased trade power and efficiency)
- Colonial Ruler (bonus to colonial growth and tariffs)
- Diplomatic Thinker (reduced diplomatic tech cost)
for MIL
- Infantry Reformer (increased infantry power)
- Cavalry Reformer (increased cavalry power)
- Warfare Reformer (increased artillery power and siege efficiency)
- Military Reformer (reduced military tech cost)

Also, note that you can use advisors to change your country modifier step.
Level 2 advisor gives you lvl 2 step, if your ruler skill is below 2.
Level 3 advisor gives you lvl 3 step, if your ruler skill is below 3.
If you have both level 3 advisor and ruler skill = 3 - you will have lvl 4 country modifier step ( which is the first positive step, as you already know).

Since v0.6a Feudal, Administrative and Despotic monarchies have different modifiers:
Feudal: weak economics, more diplomatic upkeep, cheap army with strong cavalry. Vassals mood, which depends on your ruler's legitimacy and prestige. Very weak colonial maintenance.
Despotic: more dependency on your ruler stats, expensive advisors, well-rounded country in case of a strong ruler. Weak colonial maintenance.
Administrative: Strong economics, bonuses to fleet and trade, expensive and moderate-sized army. Extra advisors at cheap cost. You are supposed to have at least lvl 2 advisors, otherwise you will suffer maluses in corresponding matters. Efficient colonial maintenance.

WHAT IS RULER EDUCATION ?
Every monarchy in game will have event for every new ruler. On this event you'll be able to choose from 4 different types of education: Administrative, Diplomatic, Military and Basic.
First three types, besides from giving you specific bonuses, also add +1 to corresponding ruler skill.
Also, after some time, your ruler can improve his skills. Firstly, he will sharpen his education, which will improve his bonuses. And secondly, usually after 15-25 years of reign, he will be able to master his education, which will again grant your ruler +1 to corresponding stat.
Basic education gives your ruler all-round bonuses, but it can't be improved.

HOW DOES AI CHOOSE HIS EDUCATION AND SPECIALIZATION ?

AI in my mod doesn't choose anything blindly!

Few examples:
• If AI ruler has 2-5-5 stats, 88% that it will choose administrative education, and have 3-5-5 stats, and 12% to choose dip or mil education. There is 0% chance to pick Basic Education if any of AI ruler skill is less than 4.
  
• If AI ruler has 0-2-5 stats, it is 93% to increase stat=2, and 0% to increase stat=0 (as there is no point in that)
  
• If AI ruler has 1-2-5 stats, it is 65% to increase stat=1 and 33% to increase stat=2.
  
• If AI ruler has 4-5-4 stats, it is 63% to choose Basic Education and 37% to increase one of 3 skills.

Also, I prevented AI from choosing useless specializations, like Grand Admiral for countries with less than 3 ports, or Artillery Reformer before 1570.

HOW DOES MY RULER OBTAIN TRAITS ?

There are plenty of traits in Ruler Traits mod. Most of them are based on Crusader Kings 2 traits, other are made by me.
The chance of getting a specific trait depends on many factors. These factors are absolutely logical, and you can predict or even take some actions to improve the chance of obtaining one, without looking through the mod code.
Let me show you an example on trait Cynical:

First of all, you won't get that trait if you already are Just, Zealous, Humble, Celibate or Imbecile (btw, Imbecile blocks almost every other trait)

If you don't have any of these traits, MTTH for Cynical is 2500 months.
x10 mtth (25000 months) if you are the Defender of Faith
x10 if you have unlocked Religious Ideas (seems logical to me)
x0.8 (2000 months) if you have DIP education
x0.8 if your government is republic
x2 if you are the emperor of HRE
x3 if you DON'T have Innovative Ideas unlocked (otherwise it is x1)
x0.9 for Spymaster lvl 1
additional x0.9 for lvl 2
additional x0.8 for lvl 3
(that means 2025 for lvl 2 and 1620 for lvl 3 )
x0.5 if Papal State is your rival.
Let's imagine that you are playing Milan, have lvl 2 spymaster, chosen MIL Education, unlocked innovative ideas, have papal state as your rival and you are the emperor of HRE.
MTTH for gaining Cynical will be 2500 x 2 x 0.5 x 0.9 x 0.9 = 2025.
Not a great chance to get that trait.

If you've chosen DIP educ. instead and haven't been the emperor, mtth would be
2500 x 0.5 x 0.9 x 0.9 x 0.8 = 810.
And that gives you a significant chance that your ruler will become cynical.

Other traits' MTTH can also be modified by having other traits, by your culture, technology type, being specific country (NOBODY EXPECTS THE SPANISH INQUISITION!), prestige level, being at war, current year, ruler stats, ruler being general, religion and many else.
I develop traits system to work in realistic way as much, as game's engine allows it. Still, I always balance it, and if you have often unrealistic trait obtainment or some suggestions - feel free to tell me about it in comments or Feedback!