I think fish oil or omega-3 supplements are really the best ones you could use. Not only will they make your skin better, they have also been shown to make all kinds of improvements in your health, as well as your brain. They can help decrease depression and increase concentration. Basically, they are close to a miracle pill.
It's unfortunate that everyone seems to know that now, because the price of them seems to have increased a lot lately. But I still try to take them regularly.