You can get a really convincing, yummy, "store-bought-like" Ranch by mixing yogurt and sour cream(50/50 ish) and then adding dried dill weed, garlic powder, parsley flakes, and dehydrated onion plus salt to taste. I don't measure anything either, just mix to taste. Thin with milk, cream, or buttermilk. I don't know if you do store bought mayo, but adding some of that makes it even closer to commercial Ranch dressing.
Honey Mustard is really easy to... Mustard, honey(or maple syrup is good too!), and some vinegar and oil.
Another that is good, though I have no idea what to call it, Asian style considering the ingredients I suppose... About three tablespoons of miso, three tablespoons of tahini, few tablespoons of lemon juice, some diced green onion and then water until you reach the consistency you like. I LOVE this one. It's awesome. If you mix it thick(less water) it makes a really fabulous dip.