The supplement industry is a Wild West frontier town and the lawmen - the governmental bodies and professional associations tasked with making recommendations and some sense of it all - are often negligent, overcautious or incapable of differentiating bad actors from good. Not to mention a mainstream media with a penchant for alarmist nonsense clouding it all and industry marketing that targets our insecurities, fears, hopes and dreams with hot models and amazing promises. The US RDA also tends to recommend sub-optimal doses of core nutrients predicated on maintaining sedentary existence and minimal function rather than thriving health and living la vida loca.
Based on my reading (two smart, approachable sources are Examine.com and Dr. Rhonda Patrick if you don't want to dig through PubMed) and using a cost/benefit epidemiological perspective, these are some of the supplements that may be worth your time. You may be deeply disappointed to find a lack of recommendations for Weight Gainer 2000 and ULTRA-RIPZ-CUTZ FUEL, but I'm not selling anything.
I'm interested in proven effects in human subjects, safety, ease of use, cost and tangible benefit. While the best supplement plan is a broad diet based on whole foods - and your first choice should always be finding a plant or animal based source to address your deficiency or provide some metabolic boost - it can be difficult to optimize for that while balancing work, family, exercise and watching House Hunters International.
Caffeine is one of the most well-studied, effective ergogenic aids around. I recommend getting it through tea or coffee, not sugary energy drinks. Caffeine increases athletic performance significantly for both endurance and strength athletes, reduces fatigue and aids cognition. Taken chronically in reasonable doses, it has useful long term health benefits. However, our bodies quickly build tolerance to its activating effects and athletes who wish to use caffeine for specific training or competition should cycle it for optimum effect.
Protein supplementation makes sense if you're not getting all of your protein requirements through whole food, are training hard, or you want to move from a heavily carb-based diet to a more balanced approach. Excess protein is benign unless you have major liver/kidney issues or are a special population. I take it in the morning and after a workout (sometimes I split the portion - half before, half after). There are plenty of good options to choose from. I just ordered some Dymatize Iso-100. Over time, I've moved from Complete Nutrition Solution type protein drinks (Met-Rx etc) to the purer stuff with no carbs, no fat, no extra boosters - just whey protein and some taste enhancements. There's some debate as to whether whey is better than casein. I don't care.
I've never taken creatine, but I'm certainly open to it and may use it to overcome a future sticking point. Creatine is a proven strength builder with a well tolerated profile demonstrated over decades by hundreds of scientific studies and hundreds of thousands of users. The NCAA bans it from being given to athletes (though they may use it on their own dime) because of "safety concerns" (better ban eggs, fish, game meat and steak too) and some "authorities" have spoken of its possible dangers. Sports nutritionists know better. Read this other rebuttal and click on the sub-heading above for Examine.com's deconstruction of the creatine mythology. Creatine makes you stronger and its only irritating, though uncommon side effects, can be overcome by drinking some water and taking it with food.
If you don't get enough fatty fish consistently in your diet, it makes sense to supplement with fish oil to reduce systemic inflammation, one of the real sources of mischief in our bodies that has implications far beyond muscle soreness. You probably saw the alarmist media reports about Omega 3s and prostate cancer. Please read this: Does it cause prostate cancer? The study was deeply flawed and the media's conclusions were irresponsible.
I take Nordic Naturals. Expensive, but I'm leery of some of the cheaper brands.
A large number of us walk around with Vitamin D deficiencies. Much of that is attributable to lack of sunlight exposure (if your ethnicity provides natural sunscreen be aware) and its rarity in staple American foods. The daily recommended levels of Vitamin D are woefully low - 300-800 IU - but it's not toxic until 10,000 IU and you can very safely do half of that. That's what I do.
Note: the older and fatter you are, the more you need to take to overcome lack of bioavailability.
ZMA (Mag/Zinc/B6 Complexes)
Half of us suffer from a magnesium deficiency. Magnesium is key to mitochondrial health and if you're feeling listless, a lack of mag could be the culprit. If you already eat tons of almonds and spinach, you're fine. If you don't, you may need some help. The US RDA is 400 mg/day and I'd triple that if you're active and get sweaty a lot. Alcohol doesn't help things either. The variety of mag you use matters, as well. Zinc is an immunity booster which can boost deficient testosterone levels modestly. Within a normal range of testosterone there is no real benefit to boosting levels. The benefit is if you can address a deficiency.
Potent anti-inflammatory. Works best when administered with black pepper. I should probably start taking them again.
The gut biome is one of the most interesting frontiers in health. Fermented, live culture foods are the way to go and I don't know enough about that supplements to recommend anything specific.
A convenient fiber source. Has the benefits of any other healthy fiber source.
Sorry you didn't find any Cut Glutes Juice in my recommendations or supplement industry mainstays like CLA, L-Carnitine, or L-Arginine but I'm afraid double blind randomized trials haven't been kind and whatever modest effects they have don't translate to tangible benefit. The next creatine could be out there hidden in all of the nonsense and placebo effects, but until the science catches up and demonstrates safety and efficacy, save your money, try to eat wisely, supplement on the margins and keep it simple.