Most played cards in Gruul:

5 Decks
Lightning Bolt
16 copies - 3.2 average
Manamorphose
16 copies - 3.2 average
Seal of Fire
16 copies - 3.2 average
Copperline Gorge
16 copies - 3.2 average
Lava Dart
16 copies - 3.2 average
Mishra's Bauble
16 copies - 3.2 average
Light Up the Stage
16 copies - 3.2 average
Soul-Scar Mage
16 copies - 3.2 average
Tarmogoyf
16 copies - 3.2 average
Monastery Swiftspear
16 copies - 3.2 average
Stomping Ground
13 copies - 2.6 average
Hooting Mandrills
12 copies - 2.4 average
Wooded Foothills
12 copies - 2.4 average
Arid Mesa
10 copies - 2 average
Klothys, God of Destiny
8 copies - 1.6 average
Tormod's Crypt
8 copies - 1.6 average
Abbot of Keral Keep
8 copies - 1.6 average
Flame Slash
8 copies - 1.6 average
Abrade
8 copies - 1.6 average
Scalding Tarn
7 copies - 1.4 average