This is as classic as you can get: 3 parts oil to 1 part lemon juice or vinegar; flavorings as desired. Use all organic ingredients.

Ingredients
1/4 C raw apple cider vinegar or fresh-squeezed organic lemon juice
3/4 C organic, extra virgin olive oil
1/2 tsp sea salt
1/8 tsp fresh ground pepper
1/4 tsp prepared mustard
Optional
Garlic cloves and fresh herbs, to taste
Directions
Place ingredients in a jar with a lid and shake. Refrigerate until ready to use. Garlic and fresh herbs should be removed after 24 hours. Shake well before using.