Use http://www.scirra.com construct2 to build a game and get it into the Store.  Use Game Salad to build a game and get it into the store.  Use Visual Studio to build an app, get it into the store.

Make money, get feedback from an audience.

Do it now.  See this blog for more information:

http://blogs.msdn.com/b/windowsstore/archive/2012/09/11/windows-store-now-open-to-all-developers.aspx