Will supplement X actually make you bigger, stronger, and faster? Or is it supplement Y?! How can you possibly tell without spending hundreds of dollars in vain?!
Related: Top 50 Best-Selling Bodybuilding Supplements
As great as it would be to pursue all athletic traits at once, unfortunately, you have to pick one or two of those goals and stick to them. Otherwise, you'll endlessly spin your wheels getting pretty good at most of these traits, but never truly excelling at one (or two). Sort of a "jack of all trades, but a king of none" if you know what I mean.
That's where this guide comes in. I'm here to discuss choosing the right supplements for your goals.
All that being said, let's take a look at some of the most common archetypes of the athletic population and pick a few choice ingredients to help truly maximize the time spent training for maximum gains.
A Word About Creatine Monohydrate
Before we go into supplemental specialization, we're going to recommend one supplement for all individuals, regardless of your chosen path of athletic excellence. You can probably guess what it is, as it's the most popular, and most successful, ingredient of all-time: creatine monohydrate.
That's right, no matter what your preference for training, creatine should be a part of your supplementation regimen. It covers all areas of fitness, and has been proven countless times to improve:
- Lean mass gains 
- Power & strength 
- Endurance 
- Muscle soreness & recovery 
Now, that that's out of the way, let's get into some specialties
Supplements for the Endurance AthleteEndurance athletes need to maintain peak levels of performance for hours, and hours, on end. To accomplish this, we need to zero in on those specific ingredients that allow these athletes to channel their inner Energizer Bunny, and keep going, and going, and going...
Beta AlanineStarting off with the king of all endurance boosters, is none other than Beta Alanine. This e binds to histidine in the body and forms carnosine, a powerful intracellular buffer that removes lactic acid accumulation. 
A's buffering capabilities offset the burning sensation allowing you to really go the distance in your workouts. Not only will your endurance levels be improved, but you'll also see notice big improvements in time to exhaustion, strength, and power. 
The clinical dose is 3.2g, but often times that's too tingle inducing for many, bordering on irritating. To circumvent this issue, split the doses into 2g pre and post workout, or any other times during the day that are most convenient.
B-VitaminsB-Vitamins are a family of vitamins the body requires for energy production and the formation of red blood cells. They are water-soluble meaning, your body doesn't store extra, as it does with Vitamins A, D, E, & K, meaning you have to "use it or lose it" in regards to water-soluble vitamins.
As you can imagine, endurance athletes sweat profusely during competition and training and will rapidly deplete levels of this crucial vitamin. Therefore, to prevent any decline in performance during your marathon-length events, it's imperative to supplement with these before, during, and after your training or competition.
Sodium PhosphateSimilar to our previous ingredient, electrolytes are another commodity endurance athletes burn through during their preparation. The most prominent of these is sodium. Copious amounts of this vital mineral are excreted by the body when we sweat.
Electrolytes play a critical role in muscle contraction as well as hydration levels. In fact, as little as a 2% drop in hydration has been shown to negatively impact athletic performance and lead to cramping as well as impaired CNS function. 
Additionally, supplementing with sodium phosphate has been shown to increase aerobic capacity and time to exhaustion.  On top of that, other research noted improvements in endurance via increases in maximal oxygen uptake and ventilatory threshold. 
Supplements for the PowerlifterPowerlifting is all about getting strong, aesthetics be damned! Based on this, we're primarily interested in those that have been shown to really bump up and individual's strength and power numbers.
BetaineBetaine, a.k.a. trimethylglycine (TMG), fell by the wayside for much of the early 2000s, but has seen a tremendous resurgence within the past year and a half. And for good reason. This derivative of choline has been shown numerous times to:
- Increase strength & power output 
- Improve endurance 
- Support creatine production in the body 
- Elevate muscle protein synthesis 
One of the newest ingredients to hit the market is elevATP®, a patented combination of "ancient peat" (fossilized plants) and apple extracts developed by FutureCeuticals. elevATP® enhances the body's production of ATP, which helps increase overall energy without the use of stimulants. It's also featured in one of MTS Nutrition's newest products, Ruckus.
The early research on elevATP showed great promise, as a single 150mg dose significantly elevated "intracellular ATP in blood cells.  As you know, ATP is the coenzyme used by each and every cell to produce energy to do work. The faster your ATP stores replenish, the faster you recover and can accomplish more work in less time!
Extra ATP levels are great and all, but what about performance?!
A recent study on elevATP® found the extract significantly increased 1RM squat and deadlift scores in strength.  Just what an aspiring powerlifter is looking for!
Joint Support FormulaThis may be an unconventional supplement to include, but when you consider the bone-crushing loads powerlifters subject themselves to, it becomes very obvious. Joints take a beating like no other component of the body, especially when training in ultra-low rep ranges.
Ideally, look for a product such as MTS Machine Motion which includes anti-inflammatory, analgesic (pain-relieving), and joint support ingredients like Hyaluronic Acid, Cissus, and Glucosamine.
Using a quality joint formula ensures a long and happy life of pain-free lifting!
Supplements for the BodybuilderBodybuilders are typically focused on one thing, gaining as much muscle mass as possible. For this reason, we're selecting supplements that help maximize hypertrophy, workout stamina, and most of all the PUMP!
Nitric Oxide BoostersIn your desire to be an elite bodybuilder, you've no doubt seen a plethora of products labeled as "Nitric Oxide Boosters." You're probably wondering why in the world you'd need to increase N.O. levels in the body?!
Quite simply having more Nitric Oxide makes just about everything better! Energy availability, endurance, and recovery rates are all increased with greater nitric oxide levels.  Additionally, it also reduces fatigue during higher rep training schemes, something all bodybuilders utilize in their never ending quest for gainzzzzzz!
All kidding aside, improved N.O. levels have far too many benefits for you to not include it in your supplement regimen. To maximally increase levels, look for a supplement with either:
- 6-8g of Citrulline Malate
- 3-4g of L-Citrulline
- 1g Agmatine
- 1-2g Nitrates (depending on what form)
BCAAsThe goal of all bodybuilders is to build as much muscle as possible in the most effective manner possible. This means keep net protein balance positive, so your body is in a constant state of muscle-building, and not muscle-tearing.
BCAAs should be at the forefront of all bodybuilders list of supplement goodies. They've been shown time and again to drive muscle protein synthesis via stimulation of the mTOR pathway.
Additionally, incorporating BCAAs into your pre, intra, or post workout supplementation protocol reduces muscle soreness and speeds recovery. 
To get the true benefits of this ingredient, look for at least a 5g dose of BCAAs in your supplements!
Phosphatidic AcidA rarely discussed ingredient, phosphatidic acid (PA) is a phospholipid which you'll find as part of every cell membrane in the body. Without getting too deep into the science (trust us, it's dizzying!), realize that PA directly activates mTOR, which drives muscle growth!
Aside from increased lean mass gains, PA also reduces body fat, lowers cortisol levels, and increases strength.  These are all traits an aspiring bodybuilder wants to maximize when training for hypertrophy.
The dose need to reap the benefits of Phosphatidic Acid is 750mg, so keep an eye out on the label for how much a particular product has!