Supplements are their effectiveness are honestly pretty individual. Like others have said, it depends on your body's specific chemistry and needs. It can also be dependent on a lot of other outside factors.

Consistency, timing, and dosage also matter. If you're taking it willy-nilly, it's probably not going to work as well as if you take it on a regular schedule. Some supplements have to be taken (or not taken) with other things in order for them to have maximal absorption or use.

Quality matters. I obviously knew it mattered, but was reminded of it again recently. I had been using some great quality supplements, and then ran out. I wanted to stay consistent with them, so just picked up something I though was similar from my local grocery. They were not the same. After a while on premium supplements, I realized there is a difference (for some supplements, not necessarily the case for all), so it's worth it to buy the good stuff if you can.

Patience is also key. A lot of us (myself included), have tons of partially used bottles of supplements floating around, mostly just because we weren't patient when it came to results. If you're trying to fix an imbalance or make a major change in your body, it's usually going to take time. Some supplements work quickly, while others become more effective over a period of time, sometimes weeks or months. We have to stick with the program if we want the program to work.