There are actually ways of acquiring users just by staying inside Facebook and not spending any money. Have you tried those? I took the Find Me Gluten Free Fan Page from 800 to over 23,000.
Let me know if you want to hop on a call.
Using your Facebook page as a way to provide actionable valuable content and resources for your audience is always one of the best way to grow organically for "Free" .. now when I say for "Free" you will need to invest time in content creation for your page. I would start with great content and have your page grow via organic likes and shares BEFORE I would look at getting more "Users" ... without content an influx of new users will be wasted and they will not stay and engage for long.
For contesting apps that drive Facebook users and also can capture additional information (email etc.) we use Offerpop.com for this. Of course any software alone won't cut it.. you need a real contesting and promotions process to use apps like this to help gain REAL likes/users.