Who I did and plan on doing again:
IK: Hinoka!Matoi
Why: gorgeous, scarlet Red head, beautiful Dragon blooded princess great supports with Kamui, make great marriage couple!
IK:Orochi
Why:Gorgeous, purple hair, beautiful noble women great supports with Kamui learn deep parts of her character and of her family, make great marriage couple!
IK:Azura
Why:Obvious choice, Azura is beautiful, great marriage couple, great supports, plus the paired IK ending!
Hoshido:Kagerou
Why: hot ninja nuff said, waifu material and high strength Kagerou!Kanna.
Hoshido:Nishiki
Why:cute pairing, can have 2 Fox/dragon children!
Hoshido:Tsubaki
Why:nice supports and can mother Matoi and can still be a princess + part dragon!
Nohr/IK:Camilla
Why:funny supports doesn't disappoint!, she's gorgeous, I made her wishes come true! and Camilla!Kanna.
There's more I did but overall all the pair's I did for myself are all equally great.