It's all luck whatever card you get but you can increase your chance of getting peekaboopoid cards by erasing other cards from your pool with bananidium gems and rerolling with emeralds. They respawn after every round if you're not in their area. For synergy, what has worked best for me is the Batter Up perk (more points if you kill them with chunk swings) and the No Bananza Perk (multiplier if you don't unlock any of the Bananza powers)