In a large mixing bowl, combine the shredded chicken, chickpeas, celery, red onion, and parsley. Add optional ingredients like bell pepper, cucumber, or feta if using.
In a small bowl, whisk together the lemon juice, olive oil, salt, and pepper. Add optional Dijon mustard, garlic, or oregano if desired.
Pour the dressing over the chicken and chickpea mixture, starting with about three-quarters of it.
Toss gently until all ingredients are evenly coated with dressing.
Taste and adjust seasoning with additional salt, pepper, or lemon juice as needed.
Refrigerate for at least 15-30 minutes before serving to allow flavors to meld.
Serve chilled or at room temperature. Garnish with additional fresh herbs if desired.