In a medium bowl, toss the arugula with 2 tablespoons of the dressing to coat. Arrange the arugula on a large platter as abed for the other ingredients.
In the same bowl you used for the arugula, stir together the tuna, lemon juice, and dill, and season with salt and black pepper.
Arrange the tuna salad down the middle of the platter over the arugula. Arrange the veggies, chickpeas, avocado, and grapes in individual rows alongside the tuna.
Drizzle the remaining 2 tablespoons dressing over the salad and enjoy!