In a small bowl, whisk together the olive oil, vinegar, and mustard until emulsified. Season with salt and pepper to taste.
In a large bowl, toss together the arugula and farro. Add the prepared dressing and toss until everything is coated.
Add the celery, bacon, green apple, and red onion to the farro mixture. Gently toss to combine. Place salad into the desired serving dish and dot with the goat cheese. Serve immediately.