Okay, we're going to walk you through this.
1) Get a small bowl out of the cupboard.
2) Pour some oil into the bowl. Olive oil tastes good and is a common choice. Anything will do, though.
3) Pour some acid into the bowl, probably about 1/3-1/2 as much as you did oil. No need to measure, that's just complicating matters. Delicious acids: balsamic vinegar. Lemon juice. Apple cider vinegar. Red wine vinegar. But use whatever you have. Lime juice. Herb vinegar. Hell, white vinegar for cleaning is better than Kraft. Whatever. I have used salsa (tomatoes are acidic).
4) Season with salt and pepper.
6) Drizzle over salad (but not more than a few minutes before you want to eat it, or it will wilt). Toss (or don't bother, seriously). Eat delicious salad.
If you made too much, put the rest in a jar and shake it up when you want to eat delicious salad again tomorrow. But this is so, so, so very easy to "make" that you can really just do it fresh every time you have a salad. Why is there bottled salad dressing? Why?
7) If you're the sort of person who is dismayed that the dressing you just made is not sweet like Catalina (and sometimes I am), you can add a little honey or maple syrup before whisking. Granulated sugar does not work so well. Anything liquid is okay, though. I've used corn syrup (shh). I've used the raspberry Italian soda syrup that my daughter bought for making sno-cones four years ago. Whatever.
8) Add a little mustard with the above sweeteners. Voila! Honey mustard dressing.
9) If you like your dressing creamy, you can add a small spoonful of sour cream or mayonnaise. This works well with the salsa I mentioned before: Southwestern dressing!
10) Add soy sauce to your dressing instead of salt-- voila! Asian dressing! Using peanut or sesame oil here works well, as does a sprinkling of powdered ginger. Rice vinegar can be a good acid. But don't be afraid to mix and match: soy sauce, lemon, and olive oil makes a perfectly respectable dressing.
I guarantee you, once you get in the habit of dressing your own salads with whatever you have lying around in your kitchen, you will feel really stupid for ever buying bottled dressing. It's not more convenient. It isn't cheaper. And it doesn't taste better. Who convinced consumers that they needed Kraft French Dressing and Hidden Valley Ranch? We Americans are a bunch of dumbasses. That is all. Open your cupboard and take back your salad. Peace.