You spend 1M daru for a random skill. If the random skill is the same as old skill it should be +1% to it. Otherwise you will not get it until you fill then enlightenment bar. I think once it is full it takes one more time to guarantee a + next level (actually 6M needed). Each level adds 1%, I am guessing. I heard someone with a level 3 was 3%. FYI level 3 is 10.
So skip enlightenment unless your troops are at their max level. It is really not worth it. The 2% of [insert name] does not amount to much at all. so 2% of 6,000 = 120, a bit of a joke for all that daru.
I am unsure if trying for level 3 means all the random skills are lvl 2 or 3. Each troop can only have 1 enlightenment skill so far.