Help me build iOS App

By telling me everything that I need to know.

So, I have Mac and I downloaded Xcode.

How do I start?

My app will be kinda of social network. People will connect their Facebook accounts (Do I need any licence for that?) to my app so that their basic info and picture could be linked on their profiles on my app.

App is about ranking people.

Do I have to buy some servers for this? Is website necessary (This is not the problem)?

Do I have to pay someone to put my app on Appstore?

What code language do I need to learn? There are about 5 people in my team, so that won't be the problem.

etc.

I will appreciate your help.

Thanks allot.