I learnt to make vinaigrette when I lived in France 15 years ago (feeling old now!) I even kept my Maille mustard jar and lid to make it. Memories :)
So after my return I did revert back to the supermarket bottle stuff but in the last few years, have only used home-made and love the difference. This is the basic version to which all sorts of herbs can be added for variety.
1 Tablespoon acid (vinegar or lemon juice)
4 Tablespoons olive oil
1 teaspoon mustard
Whisk or shake all ingredients together. Depending on the desired consistency, water can be added to thin it.
Now I want to learn how to make real mayonnaise.