Take caffeine pre-workout, definitely. It is confirmed that it increases muscle strengh and endurance and decrease muscle fatigue allowing you to workout with great intensity. Also it's a nitric oxide booster and increase blood flow into muscles.
I personally take around 150-250mg caffeine before each workout alongside other things like: L-Tyrosine, Huperzine A, BioPerine with few others. Only reason I mentioned other ingredients because after workout when I get back to my lab and start grinding it gives me focus and drive throughout the day to get things done.
Some people can't tolerate caffeine as well as others though. Take some of it before workout and watch your heart rate closely if it's goes really high. Green tea is definitely an option.