Dressings are so quick and easy to make, I don't understand the ubiquity of the bottled versions. The only skill you need to master is adding the oil slowly enough to ensure a stable mixture. Worst case, even if it goes wrong and your oil and vinegar separate, you just have to shake the dressing vigorously directly before serving. It will still taste great!
1/4cred wine vinegar
fresh ground pepper to taste
Add all ingredients except olive oil to a blender.
Blend on high until no shallot pieces are visible.
Add the olive oil in a slow drizzle while blending continuously.