Difficulties with the promotion of the application on FaceBook

Good day. After adaptation of the application from the Russian soc. networks in FaceBook immediately raises the question: "How to promote?". From my own little experience it turned out the following:

• Paid advertising: For 100 clicks - 20 users, that is, only 20% of those who are interested in advertising reach the application itself (although this flash application is more than 600 kb, you may not just wait for the download), and this is at a cost of $ 0.5 per click
• Invitations: Only 4% accept invitations (several accounts are used - more than 1000 “friends”), but the average statistics for all Facebook applications is 74%
• The same application in our networks is gaining several thousand users for the first day - without ads.

Dear users, if you have any ideas or experience in Facebook promotion, please share it (I think it will be interesting to many).
Ps If you suddenly submit paid advertisements on FB, I advise you to first look for coupons, for example on eBay.