-Just a problem which I tried to solve. Was searcing for one but didnt found any good solution.
- Lack of research, just creating app is not enough, you have to market your app. Also, Lack of time was my another problem
I used to do just Java and knew no C or C++. Below are the references that best helped me to understand the programming philosophy of Objective-C (it's easy to learn the syntax, but why code is being written a certain way is different).
Programming in Objective-C (5th Edition) by Stephen Kochan
CS193P: Developing Apps for iPhone and iPad (Stanford, via iTunes U)
For an Objective-C book pick up: "Programming Objective-C" (5th edition already!) 
Fresh book recommendations delivered straight to your inbox every Thursday.