Most played cards in Gruul:

5 Decks
Chain Lightning
20 copies - 4 average
Taiga
20 copies - 4 average
Kird Ape
20 copies - 4 average
Lightning Bolt
20 copies - 4 average
Argothian Pixies
18 copies - 3.6 average
Giant Growth
16 copies - 3.2 average
Llanowar Elves
16 copies - 3.2 average
Red Elemental Blast
15 copies - 3 average
Erhnam Djinn
14 copies - 2.8 average
Strip Mine
12 copies - 2.4 average
Whirling Dervish
12 copies - 2.4 average
Scryb Sprites
11 copies - 2.2 average
Berserk
9 copies - 1.8 average
Shatter
9 copies - 1.8 average
Avoid Fate
8 copies - 1.6 average
Black Vise
8 copies - 1.6 average
Scavenger Folk
8 copies - 1.6 average
Sylvan Library
8 copies - 1.6 average
Blood Moon
8 copies - 1.6 average
City of Brass
7 copies - 1.4 average