i tried many complicated strategies but i found that if you upgrade goblin health and unit cap then use shock on the right towers then you can just send out only goblins and get gold almost every time.
check this out!!!!!!!!!!!!||R|||-138,154,145,179,46,165,p,0,0,0,1,-137,154,145,245,31,5,p,0,0,0,1,-137,155,145,173,162,224,p,0,0,0,1|-73.95|210.45|45.7|120||
 "Villainous"){kind=icon}
 "Gravitee 2"){kind=icon}