Super Brain Yoga is actually pretty good. Course, if you have little energy then I'd definitely recommend to go very slow. Otherwise you'll burn yourself out and stop exercising. Just one or two squats per day should be fine IMO/IME and then can go up from there.
The way they say it works is it pushes the chi/prana up to your brain. Like a pump. First couple times I tried it I became very dizzy so another reason to go slow. Have to follow the instructions perfectly though and make sure feet are firmly on the floor.