Most played cards in Humans:

1 Decks
Dromoka's Command
4 copies - 4 average
Flooded Strand
4 copies - 4 average
Warden of the First Tree
4 copies - 4 average
Thalia's Lieutenant
4 copies - 4 average
Reflector Mage
4 copies - 4 average
Windswept Heath
4 copies - 4 average
Collected Company
4 copies - 4 average
Llanowar Wastes
3 copies - 3 average
Transgress the Mind
3 copies - 3 average
Lambholt Pacifist
3 copies - 3 average
Thalia, Heretic Cathar
3 copies - 3 average
Botanical Sanctum
3 copies - 3 average
Anafenza, the Foremost
3 copies - 3 average
Gideon, Ally of Zendikar
2 copies - 2 average
Heron's Grace Champion
2 copies - 2 average
Dispel
2 copies - 2 average
Abzan Falconer
2 copies - 2 average
Arashin Cleric
2 copies - 2 average
Disdainful Stroke
2 copies - 2 average
Heir of the Wilds
2 copies - 2 average