I never bought salad dressings. I make it on my own. Italian Vinaigrette is my favorite. It is simple and delicious, not to mention healthy. Simple mix white vinegar and extra virgin olive oil at 1:3 ratio. Then add salt, pepper and any spice of your choice such as thymes. Shake well. You are ready to go.
If you feel like having Japanese food. You can make your own Japanese soy sauce dressings, too. Using the Italian vinaigrette made earlier, add soy sauce (1 portion), sesame oil (0.5 portion) and sesame seeds. You can also add mayo. That last ingredient is absolutely optional, though. It is that simple.