In my opinion pre-workout supplements do not help in long-term goals. Yes, you feel stronger but those CNS gains you get are just temporary and do not translate to more gains in the gym. This simply means, that if you lay off the preworkout, you will lose all the gains you made with it, so its just useless in my opinion. Best preworkout you can have is simply 5 minutes before the workout to make your mind right. Think about what you are going to do and when you are ready, step into the gym. Not a minute earlier.
Having said that, I believe that you should either go the gym with an empty stomach or maybe consume a small meal which will consist of a banana and a scoop of whey protein. Other supplements than you can buy and put into your PW shake are beta-alanine and citruline for more endurance in the gym as well as pump. For the last few months I dont have enough money do buy all that so I stick to a banana and my whey and hey..I havent lost any gains. I actually have made a lot of progress.
Finally, I would recommend caffeine for heavy powerlifting type workouts because it can stimulate the CNS safely and help you warm-up easier. I wouldnt use stimulants for bodybuilding workouts because they will hinder your performance. If you do a lot of drop sets and super sets, your heart rate will already be up, so the stimulants will cause you to stay out of breath and you wont be able to reach failure.
Thats my opinion and my current PW strategy!
#HTH!
Kostas