Workout performance?! Help?

I am 17yrs old, and due to my work and school schedule I workout twice a week. I usually lift hard, for me, and I usually workout on a kinda empty stomach, considerin my lunch woulda been like 3-4 hrs ago. I eat breakfast,snack, lunch and then workout after school on off days. I don't have a much energy so I usually drink a gatorade durin my workout. Is there somethin else I can take for workout before/during for increased energy performance? Like do I take glutamine or amino acids? Which works better? I dont want artificial things like testerone and stuff, the closer to natural the better. Thanks for any hellp