While the homemade Texas caviar dressing I make is a cinch, and since you have to use lime juice not only for flavor but to prevent the avocado from oxidizing as rapidly, I think it's just as easy to make my own dressing rather than using store bought. However, if you don't want to be bothered, you can use a 2 tablespoons lime juice + 1/3 cup Italian salad dressing from a bottle, see how it looks, and add more, if desired. I also think 1-2 tablespoons olive oil drizzled in is a nice touch but again, play it by ear and decide as you're mixing it up.