Well
@want help why don't you try heading over to the Settings>application manager>Swipe left to ALL, and clear the cache and the data stored by the Google PlayStore, Google PlayServices app, also head over to the Settings>accounts and sync> Gmail, remove the gmail account ! Restart your device and upon the restart your device will ask for Google account put all the details in it and then try opening the Google PlayStore and try downloading any app over the device. I am sure things would work out now !
PS: Whoo....
what a profile picture ! I don't know if its' good over here or not but better would be taking it down ! Anyway your wish