This is the one I have used for years and everyone loves it. I used to use balsamic, but when I discovered the loads of sugar, I stopped using it and went back to red wine vinegar, not using too much.
Olive oil (1/4 c.), a tad of red wine vinegar (to taste, maybe a tablespoon), a little water (maybe a tablespoon), squeeze of lemon, lots of freshly cracked pepper and some half & half (about an 1/8 c.), which helps it bind.
In the salad bowl, which is never washed, just wiped out, I start with olive oil and pepper, garlic, then all the accoutrements....always some kind of nut and berry with the usual: oinion, avocado, sweet peppers, goat cheese, etc.....whatever you prefer. Just before supper, add the lettuce/leaves, etc and then just sprinkle dressing on. I don't like it swimming. Toss and add feta on top.
Salad in a bag is for man types!