How can you get good vitamin advice? Because most places want to sell you a boatload of vitamins and you don’t know if you can trust them.
Talk to your doctor, perhaps? I think you’ve put your finger on the problem, which is that too many people who (claim to) know something about vitamins also just happen to be in the vitamin-selling business…
SupplementWatch has good info.
Have you tried a pharmacist or two? You might hit one that’s anti-vitamin, but my experience has been that they are helpful and knowledgeable. Not all vitamins are good for all people, especially if you are on prescription medication, and a good pharmacist can help you figure out what you need.
Choose sources that have no interest in selling a product–either vitamin supplements or books, for example.