Usually, 400-600mg a day in 200mg doses on an empty stomach. I understand from google sources, 800mg is the top amount. I'm not sure that is true for everyone.
The first of the day with coffee is good to get the day in focus, after an early lunch, then before bed. Another of the "nootropic" babies but I started using it long before this faze in mind tweaking. I don't know about now, but years ago it was suggested by doctors for panic. Wish I had used it more instead of falling into the comfort of xanax!!! Ah well, another one of those "shoulda, woulda, coulda"s. Good luck with it!