You are free to write your own tools like Slin and I did, it gives you much more power than using something existing and its a good way to increase your Cocoa skills.
And I wouldn't recommend starting with a game, start with a simple UIKit project and learn the whole UIKit lifecycle, then head over to games and engines. Why? Simple, the engine might be very powerful (I'm running out of memory before the engine runs out of FPS), but the iOS binding is really horrible, although Slin already improved it alot.

So, learn the basics on how to write a great app with UIKit/Cocoa-Touch and then learn how to write great apps with eg. isdge.