Honestly, the answer is "all of them."
But, it's how you mix clans that really counts. When you are making a dual-clan deck, the best strategy is to pick cards that can survive without their bonus, and compliment each other in some way. Your typical hand should have strong offensive cards, but offer some protection from the common strategies seen in the mode you intend to play as well.
A simple example: Putting Freaks
together works well. Jungo
life gain works well with Freaks
poison -- you can think of life gain as lowering a poison's min. (In case you don't get the concept right away: If you are playing ELO
and hit with Olga
in turn 1 and hit with Rodney
in turn 2, you do a total of 13 gap -- 11 from regular damage and poison, and 2 from Rodney's life gain. On the other hand, if you hit in turn 2 with a 5 damage card, you only do 11 gap total, since the damage caps out at min 3.) Furthermore, both clans have high natural power and attack/power manipulation abilities, which makes a Freaks
deck suitable for winning 3 rounds, even if you draw a card with no bonus. Even better: Jungo
have 5*s with decent damage AND round winning abilities, namely, Askai
... Including these cards will help your deck remain solid vs SoB, which will rob you of a lot of damage.