recently a vendor gave me free stuff and i made a mix to help me focus, and believe me, it works.
i used coffee crystals(soluble instant coffee), ginkgo, ephedra, and yohimbe. the closest thing to an extract is the coffee. i had a feeling ephedra and yohimbe might not be safe so very little yohimbe was used. there was a good amount of ginkgo and about two thirds of the ginkgo worth of ephedra.
this mix is best taken in a gelcap or just eaten like i do. if you make tea, use bigger pieces of herbs, otherwise the teabag will clog. but other than that, i think this is an effective mix