If your advertising isn't giving enough returns, advertise more. Seriously. Who is to say when it starts yielding results? See your advertising as an investment. Also, try other channels. Have you tried the free medium? They too work as well as the paid medium. The key thing here is exposure. How exposed is the medium you are using? Having answered this, Diversify. Advertise in more places. Keep throwing your net out. You may soon catch plenty of fishes. Good luck.