Well, Charlotte-Chan, at 4 or 5 servings of veggies a day - how big are your window sills?
Okay, I can see a table set in a good south-facing window as making a contribution to a person's diet. I'd stay with shade-tolerant choices, like lettuce and spinach. Even if there's a lot of light and, maybe even, a little hot and dry - the glass will cut down on usable light for growth. Still, plants can do quite well in a sunny window and make quite a bit of growth.
You may want to try some of the Asian greens - like bok choy. Leaf mustard would also be worth trying. I may start things like bok choy in my south window but these plants all go out into the open garden at my place. I can only imagine them staying in the window and doing well.
Think about sprouts. You don't need the south window, they can be grown on a kitchen counter. And, you don't need any fancy-smancy sprouter. Cheese cloth over a jar works fine. You just need to be conscientious about rinsing them with fresh water several times a day - and, using them!
You may be able to buy seed cheaply in bulk. One of my favorites is alfalfa sprouts. Maybe alfalfa is known as lucerne to you. Radish seed also makes good sprouts and there are many others! I like sprouts, not only in salads, but with cream cheese in a sandwich.
Hope others have ideas for you - Best of Luck!
We are each other's harvest; we are each other's business; we are each other's magnitude and bond. ~ Gwendolyn Brooks