Ranch Chickpea Salad Sandwiches

Name: Ranch Chickpea Salad Sandwiches
Ingredients: 1/4 cup finely chopped red onion (about 1/2 small red onion); 1 tablespoon plus 2 teaspoons fresh lemon juice; 1 15-ounce can chickpeas, drained and rinsed; 1/3 cup ranch dressing; Kosher salt and freshly ground pepper; 1/2 cup finely chopped celery; 1/4 cup chopped fresh parsley; 1/4 cup chopped fresh dill; 8 slices multigrain bread, toasted; 4 to 8 leaves Bibb or Boston lettuce; 1 ripe avocado, thinly sliced; Ranch tortilla chips or dill pickle potato chips, for serving; Dill pickles, for serving