FBStart – is the big opportunity (for some people). 
The FBStart program is for mobile startups only. 
However if that’s you, it’s a great program if you get onto it.

One of the startups I’m an advisor to, got $1,000 of free Facebook ad credit through this program. 
They signed up and got $500 credit, and then when they progressed through all the training they got a second $500 Facebook ad credit.

https://developers.facebook.com/fbstart/