Just finished a first playthrough which end at turn 80 with ending 2, pretty easy once I understand how things work, so I think I'm gonna share some of my understanding of the game and see if it help anyone who have trouble beating the game.
First, here is a list of the girl you can get :
This is my guess on how the breeding in the game work, it might not be correct:
There is a base stats for Goblin and each goblin stats is depend on their class multiplier to that based stats, to avoid confusion, let's take the starting Goblin stats as the base stats, it has 5 HP, 4 ATK, 3 DEF and 3 MAG, if you use this Goblin to breed, you can expect a HobGoblin with stats around 20HP(4x), 8 ATK(2x), 12 DEF(4x), and 15 MAG(5x), not always the case but it's always quite close.
With that being said, you should focus on raising base stats as high as you can with each generation, the way to raise base stats:
1. New Generation, each generation give small boost to all stats, I know this because I fuck the girl who give MAG, but somehow my DEF increase.
2. Fuck specific girl, each girl give boost to specific stats.
3. Eat Item, they do increase base stats while they increase the raw stats, so don't worry about new generation weaker than the previous one, for example Shaman, eating food that grant raw stats of 10 MAG, should give enough base stats to make next generation Shaman have extra 5 MAG compare to those who doesn't eat. (Also killing girl by making them 0 SAT and then fuck them will give a bone item that greatly increase all stats)
Now in term of skill, I think they are decided based on whose girl's gene on the generation, rather than the girl you recent fuck, it mean let said your Shaman has a skill Secret of Wood and Wind Pickles, but because somewhere in this Goblin generation you fucked Anvil, the next Shaman might just born with Healing Track and another skill, this will sometimes really fucked up your skill set if you been fucking girl randomly without thinking.
To prevent this to happen, use the girls with no skill (Ilari at Days 7) to make skill-less goblin, and then only have those goblin fuck the girl you want the skill to inherit onto, just remember to favorite one Generation 1 Goblin and make sure it doesn't died if you want to do this.
Now, onto the game itself, early game was a bit hard, but become easy once you get Champion and Shaman with Secret of Wood, the next challenging thing was fighting Vivian, but should be fine by removing golem with ranged attack and burst her with Shaman Magic, and after that once you breed Shaman and HobGoblin with Anger of Tree People, the game just become easy mode.
Anger of Tree People is a skill that hit all enemy with 1x MAG damage(Later replace with another skill that does 1.3x), HobGoblin has 5.0x MAG compare to normal Goblin, and Shaman has 8.0x MAG, HobGoblin has no restriction like Champion,Shaman,Paladin and Lord, so basically at that point what I do is keep breeding HobGoblin and Shaman, with both of my loot/defend roster consist of 3 Hobgoblin + 1 Shaman, 2 Hobgoblin pair with Goblin, 1 Hob Goblin pair with Hob Goblin and the Shaman pair with Shaman, with this team you can basically pillage twice, HobGoblin blow out their partner, and finish them off with Shaman, easy.
For Boss battle, switch all pairing to Goblin, then just do retreat + AoE MAG x 3 , this usually wipe out the other unit other than boss, if not, just repeat again next days, they do get to attack, but all you lost is some generic goblin, sometimes the HobGoblin / Shaman if they decide to focus on one target, but it's alright, it's only one.
This Tactic work till the last Boss Patrizia, burrow defend is even easier with trap healing back your goblin every turn.
Now onto the battle itself, you had main unit and you can pair it with side unit, not sure how the calculation work but side unit do greatly affect your main unit, a HobGoblin with Champion as side unit can hit enemy for 50+ when usually only hit for 12+, but be aware that each side unit basically act like a shield with 1HP each, you have 10 Champion as a side unit, they hit your main unit for 10 damage, all your Champion died, unless you can heal them back up.
This is why I don't like to use Champion, his defend are low, and he has no MP to use any kind of healing, if you want someone who can fight in front, use Paladin.
Thats all I can think off for now, hope it help.