Here are some supplement recommendations for athletes seeking to maximize Hypertrophy. With Hypertrophy we are trying to maximize the acidic environment to induce as much damage, cell swelling and hyperemia as possible. What can we take preworkout to help this along?

Primarily, we will want to look at things that shuttle nutrients and blood into the muscle.

Citruline Malate: reduces fatigue and improves muscle endurance. More effective than Arginine. Arginine actually decreases GH during your workout when taken pre exercise. Arginine is best used before bed.
Antioxidants : Alpha Lipoic Acid, grape seed extract and CoQ10 improve mitochondrial function and will allow for more blood flow to muscles during training.
Beet Root Powder: Vasodilator, will induce a pretty gnarly pump.
Neurotransmitter boosters: these will be important for anyone that has a hard time getting amped up to train. I advise against taking caffeine as a pre workout before Hypertrophy sessions because caffeine is a vaso constrictor. That means that taking caffeine with nutrients to chase the pump is a bit futile. There is a trade off for sure. If training without caffeine leads to a shit workout, then it may be worth your while to take caffeine instead of some of the vasodilators. Taking both at the same time though, to me, is a waste of money.
BCAAs: provides energy and will prevent muscle protein breakdown during training.
Creatine: will help sustain energy levels throughout your sessions and get more fluid into the muscles.