Sprinkle chicken with garlic salt and chili powder. Spray a skillet with cooking oil. Cook chicken strips over medium-high heat until brown and well cooked.
In a small bowl, mix Ranch salad dressing with red salsa. In another medium bowl, mix shredded lettuce, black beans, corn kernels, green and red peppers, stirring until everything is well mixed.
In a salad plate place a tostada shell, lettuce with black beans, corn and peppers and pour half the dressing. Then place another layer with the chicken strips and pour the rest of the dressing over the chicken strips.
Top with chopped tomatoes, chopped green onions, avocado slices, chopped cilantro, light sour cream, salsa and grated Monterey cheese on top, if you like.