Combine the ricotta, sour cream, chile paste, oregano and 1/2 teaspoon of the salt in the bowl of a food processor. Puree until smooth. Remove to a medium bowl. In the same food processor, combine the beans, pesto, 2 tablespoons of the lemon juice and 3/4 teaspoons of the salt. Puree until smooth. Spread the bean mixture on the bottom of an 8-inch baking dish. Pour the ricotta mixture on top and spread evenly.
Sprinkle the Parmesan over the ricotta. Sprinkle the arugula over the cheese layer. Sprinkle the sun-dried tomatoes and olives over the top. Refrigerate until ready to serve.
Just before serving, toss the avocado with the remaining 1/4 teaspoon salt and the remaining 1 tablespoon lemon juice and spread evenly on the top. Serve with pita chips and celery sticks.