I would like to add my personal viewpoint to this supplement thread:
Fish Oil - especially cod liver oil - is the primary supplement for one to take. It has many necessary fats and vitamins, but most importantly, it contains incredible amounts of naturally potent Vitamin D and Vitamin A (and their respective metabolites.)
Every single cell in the body has a vitamin D receptor. This is like a key for every cell to grow and regenerate. All other supplements will become much more potent when using this one as the primary.
From what I have seen, depending on the individual, it can take up to 3 months and generally 4 weeks to really start noticing the benefits.
Vitamin D (plus A) is also an important link to testosterone function within the body. That should be important enough.