In a screw-top jar, combine olive oil, vinegar, sugar, and garlic. Season to taste with salt and pepper.
In a very large bowl, combine bread, tomatoes, cucumber, celery, onion, and basil leaves. Cover and shake dressing to combine. Drizzle about half of the dressing over the salad mixture and toss. Let stand for 15 to 30 minutes at room temperature. Top with ricotta and drizzle with remaining dressing. Makes 6 main-dish or 10 side-dish salads.