As for Monkey Boy, try to reroll like Slashley and Jessa reccomend. It doesn't matter for SSR kami you get since it will appear along the way.
As for now, the only thing you need to do is to looking those 140% (Levi/Cer/Nid/Han) and 100% (Mana/Anu), but their base isn't fully 140%/100% since they require same element eidolons. Former 100% (Hrae/Ru/Bel/Ki) also helps tho, but not as powerful as 140% but their base is at 100%. Hope this helps

(and good luck if you're also trying to unlock those T4 souls)