Accidentally deleted Google Play Services, now no Google supported app works
First, you can install Google Play Services APK, which you can find in the xda-forums. This should normally work.

If nothing else works, you can do a Factory Reset. Unfortunatly, this will delete your Data on the Phone, so i recommend making a Backup.

EDIT:

Go to https://play.google.com/store/apps/details?id=com.google.android.gms with your PC, log in, click install, and choose your phone.