No can of pills will ever replace food. After nearly 30 years of competing and having access to all the free supplements I could ever want, I've found that there's very little that actually helps your progress, assuming you've got your meals right. Dieting is a different matter, but on a well-fed mass program, save your money for food.
The most important aspect of supplementation is correcting any vitamin or mineral deficiencies, which are rare but can exist. A blood test can help identify those. On the other hand, mega-dosing a bunch of vitamins is not only worthless, but also potentially harmful. Nearly all the scientific research touting the benefits of vitamins has been done on vitamin-deficient subjects, so claims are made based on those results. Very little evidence exists showing any benefit of mega-dosing for non-deficient subjects. However, even scientists who have read and agree with the research still take a basic multi-vitamin (100% RDAs) just because it's hard to know where the deficiencies may lurk. I do the same thing for no particularly good reason. Beyond that, I focus most of my supplementation around my workout.
My pre-/intra-workout drink is a cooler full of ice water, carbs, BCAAs (20 g), creatine (10 g) and a mineral/electrolyte tablet (Nuun tablet). My post-workout drink when I was competing was whey isolate and carb powder, but now it's just a large shaker of chocolate milk, which serves about the same purpose. I always have some quick post-workout nutrition and then eat an hour after I train. I'll also admit to being on the bandwagon for a few other supplements that I've convinced myself will benefit my long-term health, so I take 4,000 mg vitamin D3, 300 mg CoQ10 and 2,000mg of Omega-3s daily. I also used to take ZMA before bed when I was competing. That's about the extent of what I'm willing to admit I spend my money on, although I often question the value of the investment because when I miss a week or two of any of the above, I don't notice any difference in performance.
But if I miss a meal or two or have a short night’s sleep, then I immediately feel it in my workouts.