TL;DR: Supplements are mostly a waste
Exceptions I am aware of:
Everything else that shows a benefit turns out to have cohort issues IME. In other words only deficient people show a benefit. B12 or Vitamin C are good examples. I've been through much of examine.com and haven't found anything else worthwhile supplementing. if anyone spots anything feel free to post it.
I was wondering why no fish oil, but examine.com finds rather little effect from it-- there's evidence it's good for lupus and for major depression, but it doesn't seem to do much for people in general.
Examine.com's Guide to Supplements.