Tar backup will never return the server to orginal state. It is like copying your files to another folder.
What you need to do is, identify the files you need to backed up. Then make tar file (it is like a ZIP file in windows).
If you ever need to restore, just extract the files from tar file, then replace the files on server with it.
You can set a cronjob to make tar file daily, so you will have daily backup, that can be uploaded to Amazon S3, Google Cloud or Dropbox.