You can farm for gralats (in game currency) by buying a house with grass in it.
After you buy your house, go to the Belle Isle Garden Shop and purchase some 
fences that will cover the front part of the farm.
align the fences.
Buy bombs.
throw bombs into the grass!

do NOT collect the gralats when the appear. instead, let them stay there and keep throwing bombs
at them. they will soon stack in value and turn into other colors.

-=GRALAT VALUES=.
Green: 1-4
Blue: 5-29
Red: 30-99
Gold: 100-999
Purple: 1000-9998
Black: 9999-Infinite