The answer is what you do best!

I have seen from programmer to UIX Engineer to Marketing or someone who dont know any of this managing App Developing Team. As any other business knowing HR and having clear vision and understanding of the industry is most important. In generally a Mobile App StartUp should not be a very big Team, I am assuming 3-10 is ideal team size. But retaining good developer and designer in most demography is a challenge. If you have not a programmer you could hire a CTO, if you are not a marketer you could hire a CMO. But to really run a company like Pro, a insider you have to have clear idea, which language, framework platform you are using, how marketing for your specific sector. You dont have to code, but you need to have basic idea, so you could at least understand your team's work load and time frame. Or you could also have a co-founder who knows what you don't.

I hope it gives you some idea. I could give specific answer if I know your specific situation.

Best of luck!

ALL OF THEM...

Remember, experience is what you get just after you need it. A lot of the lessons that you'll need to learn will be hard, SO just keep your head up and keep moving towards where you want to be.

Hey man,

I have been a mobile app start up in the past, I don't consider myself a start-up anymore as I'm profitable. My advice: you need to learn from the best. That includes Chad Mureta for apps & Trey Smith for games. From them you'll learn the basics. You''re unlikely to strike gold from your first app, you'll strike gold once you've done a bunch and understood what works and what doesn't. I insist: you need to learn from the best in the business and be around people successful in apps to share tips and strategies. If you must know, you don't need to know programming, I don't and my fellow app-entrepreneurs don't either. You're better off learning how to outsource to sites like elance & odesk. Making mobile apps is a process and you need to learn it before you can start making $

Lots of them
Ideally you should be looking to build a team to help you accomplish everything that needs to be done.
Are you a techie? A Creative? Have a business background?
What sort of app is it? A game, business or utility app?
The key areas that apply to all apps though are Business, Marketing, UI/Creative and of course tech. Then depending on the app specific skills may also be required. Game development or industry expertise