Most played cards in Gruul:

4 Decks
Giant Growth
16 copies - 4 average
Lightning Bolt
16 copies - 4 average
Chain Lightning
16 copies - 4 average
Taiga
16 copies - 4 average
Kird Ape
16 copies - 4 average
Argothian Pixies
14 copies - 3.5 average
Llanowar Elves
12 copies - 3 average
Red Elemental Blast
11 copies - 2.75 average
Scryb Sprites
11 copies - 2.75 average
Erhnam Djinn
10 copies - 2.5 average
Shatter
9 copies - 2.25 average
Whirling Dervish
9 copies - 2.25 average
Berserk
9 copies - 2.25 average
Scavenger Folk
8 copies - 2 average
Black Vise
8 copies - 2 average
Blood Moon
8 copies - 2 average
Avoid Fate
8 copies - 2 average
City of Brass
7 copies - 1.75 average
Sylvan Library
6 copies - 1.5 average
Elvish Archers
6 copies - 1.5 average