Try raising your rating as much as possible before hitting your goal. To reach your goal, raise your prices to 300 and buy the most expensive ice creams (the newly unlocked ones) then alternate between the most populated areas.
After starting the game with five of each flavor, find out the most popular one and buy those. Raise your prices to 50. Once your rating is 3%, raise the prices to 60 or 70. At a 7% rating, raise prices again to 80 or 90. Monitor your flavors constantly until you reach a 10% rating.