In a small bowl, mix together the ricotta, mozzarella, garlic, and oregano. Place the pizza crust(s) on a baking sheet or pizza stone. Brush with 2 tablespoons of olive oil. Spread with the ricotta mixture and top with grated Parmesan cheese. Bake for 10-12 minutes.
While the pizza is baking, toss the arugula with the remaining ½ tablespoon olive oil and balsamic vinegar. Remove the pizza from the oven, top with the arugula mixture, and serve.