The classic Italian salad dressing consists of three ingredients: extra virgin olive oil, vinegar (or lemon juice) and salt. The ratio is typically 3 parts oil to 1 part vinegar.
Quality extra virgin olive oil is the foundation of a good dressing. A fruity, slightly peppery oil creates a flavor layer on its own, without needing many additions.
Try different combinations: balsamic vinegar with intense Tuscan oil, lemon juice with delicate Ligurian taggiasca oil, or red wine vinegar with medium-intensity oil.