At my doctor's direction, I take a multi, vitamin E, vitamin C, garlic, and fish oil during the summer. The extras are immuno-enhancing.
My multi-vitamin is a liquid by Tropical Oasis, called All-in-One. It has vitamins, minerals, aminos, and herbs. All I can say is when I don't take it, for example I went on vacation for a week and forgot it, I immediately notice a difference in my hair, nails, and skin. It's $23 for a month supply, tastes great, and seems to really make a difference for me.
When I used to take the cheapo over the counter tablets, I really did not notice any difference. With this product it is very obviously at a minimum keeping my hair, nails, and skin in great condition.
I think for most people, a multi-vitamin is plenty.