What should kind of supplements should i take when using the gym?

None necessary: There are no necessary and few very proven supplements that safely enhance a workout. Creatine has been shown to benefit some athletes that perform rapid bursts of activity (power lifters, etc.), but there are side effects, especially if taken above the recommended amount. Caffeine, when used in moderate amounts (50-150 mg- 1/2 to 1 1/2 cups of coffee) may be benefit and considered safe for most.