Mine approach was (6 spies - 1 extra for increasing probability) Cantarella, Roderick of Dun Tynne, 2x Emissary, 2x Duchess's Informant, (1 quest finisher) Yennefer of Vengerberg, (1 game "not loser") Cahir Dyffryn and (1 combo stabilizer) Royal Decree.
I added some more cards like Defender to protect Cahir, swarm cards like Impera Brigade, Daerlan Soldiers, that bonded neutral card with camel to make Yennefer effective for me etc ... and I ended up with interesting, fun to play, casual deck, that not only did the quest, but it was also entertaining to play.