Moisturizer is the key. My secret is Vaseline. I promise this will work. As often as you can think of it, rub a tiny bit of Vaseline on your finger nails and cuticles. I keep a small tube of Vaseline in my car and rub it on at stop lights. Once you get into the habit, you won't stop.
As far as Knox gelatin ... my parents used to drink that. The purpose is to increase your protein. If you are already getting enough protein, you're probably fine.
Don't use nail polish because the polish and polish remover will dry out your nails and make them brittle. Again, moisturize, moisturize, moisturize.