Layer 1/4 cup spinach, 1/4 cup beets, 1/4 cup garbanzo beans, and 1/4 cup shredded carrots in each of 4 jars. Combine olive oil, vinegar, mustard, honey, salt, and pepper in the remaining jar; place lid on jar. Shake until dressing is evenly combined. Pour 1/4 the dressing over each salad.