Radar asks for those three fields on a manual add. Find can fill them from a listing when the show is already online. Notes, ratings, photos, and support acts can wait until the morning after.
Free accounts can log ten gigs. Most people use the first ones on shows from this year, then backfill the nights that still have a ticket stub or a photo.
Download Radar on iPhone or Android, log that one show, and the diary has a start.