Normally, you can only cast creature cards during the main phase of your turn, when the stack is empty and you have the priority
Anything fewer and you will constantly feel like you are behind the curve
From there, you can go: Orzhov (WB) : Teysa Karlov, Elenda, the Dusk Rose, tokens Rakdos (BR) : Judith, the Scourge Diva, Mayhem Devil, treasure synergies Golgari (BG) : Mazirek, Kraul Death Priest, Savra, Queen of the Golgari, graveyard recursion Mardu (WBR) : Alesha, Who Smiles at Death, Queen Marchesa, more aggressive builds Abzan (WBG) : Tayam, Luminous Enigma, Ghave, Guru of Spores, counter synergies The archetype scales well at any power level
It flavored them as helpful creatures, and it served as one of our smoothing mechanics to help players draw relevant cards