Overlap alternating tomato and mozzarella slices around the edge of a platter. Whisk 1/2c. olive oil, 1/4c. vinegar and salt and pepper to taste together in a small bowl. Combine the arugula with half of the oil and vinegar mixture in a large bowl and toss. Place the arugula in the center of the platter. Drizzle the remaining oil and vinegar mixture over the tomatoes and mozzarella. Sprinkle with the salt and pepper and garnish with basil.