Alright so here goes nothing I guess, I will try and answer all of the questions to the best of my abilities, I have played disgaea 5 for quite some time but I'm still not 100% on all of it, I've played disgaea 1 and 2 only on PC so far, so 3 4 and D2 are still new to me. (This might be a tad long, so excuse me.)
Q1: What sub-classes are best for each of the Story Characters?
: Subclasses are only used to increase your starting stats and to get evilities, it doesn't really matter what subclass you get in the beginning, the campaign is only like a tutorial where you learn and adapt to all the new mechanics, once you clear the campaign it will all be clear from there. (Eventually you want to max all of them anyway, so it doesn't really matter.)
Q2: Are their optimal combinations for non-Story Characters?
Q3: Sub-classes supposedly give your character that obtained sub-classes some sort of bonuses? What are those bonuses?
Q4: What actually gets passed down when Reincarnating?
Q5: Is there a limit to the number of reincarnations per character? Does the required mana double every time?
Q6: Is it worth reincarnating a Rank 1 Character to their Rank 6 Version when possible? Ie. Thief -> Master Thief
For example if you clear the campaign with killia, he gets 5 stars in every single sub-class from some grinding. (Aslong as you keep changing at 5 stars) and then you can just make new thief at the desired level at the desired rank. 5 stars unlocks all the ranks at the recruiter, that way you dont have to reincarnate and waste some time using them for nothing. (Unless you dont want to min/max then just do whatever you want.)
Q7: Should you reincarnate before Lv 9999 & Genuis capability?
Q8: What are the best evilities that can be purchased from the Skill Shop when it opens?
Q9: What are the best evilities for "late game"or post game? (This will probably be the longest answer so bear with me)
: Greedy Disposition (Nether Noble, Unique) - Increase stats by digits of money earned x 3%: Sell some items in carnage mode and you get atleast 30% increased stats easy. it caps at 39% when you max the digits on the gold counter.
: Twin Heads (Twin Dragon, Unique) - When attacking without moving, attack again: Its mainly used for sage farming. (You can lookup a guide for what that means.)
: Acceleration Shot (Pirate, Unique) - Increases damage dealt by panels between the unit and target by 15%: Simple and effective ways to get increased damage on something you have a really long range on. (Like land decimator, or a sniper gun character that you can, or any longrange mage.)
Mass Blaster (Sage, Unique) - Increases damage dealt by targets of the attack x 10%: Insane damage with land decimator, but with other spells it would cap at 90% (At 9 targets in a perfect square, Ha!) Good on martial 4 stage when you get it later.
: Angel Song (Celestial Host, Unique) - Increases attack of adjacent allies by 25%: Note that the attack increase isn't for the stat, but for the general multiplier. Putting these on the support characters and having them stand next to your character before attacking is an easy and rather effortless way to increase your damage.
: Assault Attack (Valkyrie, Unique) - Increase Damage dealt by panels moved x10%: Simple and effective way to use up a slot if you cant find anything better to increase damage, moving from the front to the back of someone is 4 moves, and would increase your damage by 40% minimum, if you make a build out of it you could move 20 squares then then attack for 200% increased damage. (Or more, I dont know if it caps sadly.)
: Violence (Void Dark, Common) - Increase stats by 50%, but only earn 50% EXP: The bread and butter of any lategame build, the stat increase you can have caps out at 100% so greedy disposition + this gets you to about 89% (And just put the character in the foot soldier squad and you get the cap) You dont need XP at the point when you want to use this anyway, so that that downside doesn't matter (After mastering all sub-classes and achieveing max level again.)
: Heavy Stance (Dark Knight, Common) - Increase stats by 30%, but cannot be lifted: Again just easy ways to get the stat increase cap at 100%
: Purgatory (Dark Knight, Common) - Increase damage dealt by criticals by 50%. Easy way of getting more crit damage, you want to put 100 thimbles in the curry that you get later on in the "other" slot and you will get 100% crit from it. (Just make sure you wait 100 days before eating it so it lasts for a 100 days, then make a new one when the old one is in your belly, so it goes endlessly.) 1 day is one battle basicly.
: Mana Burner (Metallica DLC, Common) - Increase ATK by 50%, but use 1% of Mana every time Damage is taken. Again this is worded wrong, it doesn't increase your ATK stat, it increases your damage, the mana burn itself doesn't matter once you've already done everything you want with the assembly, its just another free damage boost if you have slots left.
:Bodyguards (Girl Laharl DLC, Common) - Increase ATK of male units in assigned squad by 5%: Again its a very simple increase in damage, the ATK isnt the stat again its just damage increase, the wording in the english version of the game is straightup garbage sometimes, hopefully they do better next time.
You transfer this to a bunch of units in the chara world (By using the purple scroll at the end) and put everyone in the biggest squad you can find. (Probably the foot soldier squad.) and get a 95% increase in damage if they're all male, if you want female units to get the bonus you will have to use the "gender bender" evility to magicly change their gender. (It doesn't really show, you just have to know.)
:Boorish Counter (Chara World, Overlord) - Will not counter attack, but increase stats by 20%: Again its just a neat way to get to the 100% stat increase cap from evilities, just slap this on any mage that doesn't counter people anyway.
: Critical Point (Peta DLC, Common) - Increase critical damage dealt by 30% when not near enemy units Again just a nice increase in damage for ranged characters, use this aswell as purgatory for a sweet increase.
: Kamikaze: (Zeroken, Common) - Increase critical Damage dealt by 100% if target unit's SPD is higher than yours: Again this is a typo, the crit damage is granted if YOU have higher speed then THEM, this is just a free 100% crit damage increase if you have higher speed then your opponent. (Which is always going to be the case when grinding.) You aren't supposed to fight things that have higher stats then you anyway, cuz you wont win haha.
: Unconditional Love (Artina DLC, Common) - Increase ATK by 30%, but obtained HL will become 0: Again its not ATK stat, its just the multiplier, which means more damage! you dont need HL from enemies or from the bonus anyway, just sell items instead. (30% for 2 slots is neat.)
Q10: Is there a maximum number of times you can enter per reincarnation? The cost to enter resets when you reincarnate, I know that, but not much else
Continued in the next reply.