Layered Shrimp Salad with Lime Dressing

-2 lbs. medium fresh shrimp, peeled and deveinedExtra virgin olive oilSalt, red/black pepper, garlic powder, Cajun seasoning4 c. shredded iceberg or Romaine lettuce or spinach/kale/arugla4 c. cornbread, crumbled2 c. grape tomatoes, halved2 avocados, chopped1 (15 ¼-oz.) can Mexicorn, rinsed and…