Most played cards in Horde of Notions:

3 Decks
Swords to Plowshares
3 copies - 1 average
Stomping Ground
3 copies - 1 average
Scrubland
3 copies - 1 average
Sacred Foundry
3 copies - 1 average
Savannah
3 copies - 1 average
Taiga
3 copies - 1 average
Temple Garden
3 copies - 1 average
Lightning Bolt
3 copies - 1 average
Volcanic Island
3 copies - 1 average
Underground Sea
3 copies - 1 average
Tundra
3 copies - 1 average
Tropical Island
3 copies - 1 average
Polluted Delta
3 copies - 1 average
Plateau
3 copies - 1 average
Umezawa's Jitte
3 copies - 1 average
Godless Shrine
3 copies - 1 average
Flooded Strand
3 copies - 1 average
Bayou
3 copies - 1 average
Badlands
3 copies - 1 average
Hallowed Fountain
3 copies - 1 average