Press menu in the top right corner of your screen and select "Enter Coupon".

Code	Effect
BYEGSTAR	+50 Gems
Banana	+20 Gems
Beginning	+200 Gems
Biilybob	+250 Gems
Chicken	+50 Gems
Featured	+50 Gems
Feedback	+100 Gems
Fight	+50 Gems
GSTAR	+50 Gems
GUNDAM	+50 Gems
Gattch	+150 Gems
Golf	+100 Gems
Grape	+20 Gems
Like	+30 Gems
Mango	+20 Gems
Marry	+50 Gems
Monday	+50 Gems
Orange	+20 Gems
Peach	+20 Gems
Pear	+20 Gems
Pineapple	+20 Gems
Proud	+50 Gems
Real	+50 Gems
SUPERMARIO	+50 Gems
Sparta	+50 Gems
Strawberry	+20 Gems
THOUSAND	+50 Gems
Thanks	+100 Gems
Watermelon	+20 Gems
abcdefg	+20 Gems
awesome	+20 Gems
bigheadknight	+20 Gems
billyboblove	+20 Gems
billybob	+20 Gems
blackfriday	+100 Gems
fanart	+50 Gems
finalfantasy	+50 Gems
followers	+50 Gems
gorgeous	+50 Gems
happy	+20 Gems
health	+100 Gems
ilovebillybob	+20 Gems
inthebus	+50 Gems
mafgames	+20 Gems
oucharcade	+100 Gems
showmethemoney	+20 Gems
sofun	+20 Gems
wonderful	+20 Gems
zaap	+20 Gems