What experiments should I do to determine if Modafinil provides benefits for me?

Hi! Even though I am not a healthy non-sleep deprived student, I study a lot (both at the university and because of my own research). I want to take advantage of any help I could get, therefore I'm turning towards one of the popular methods: modafinil. I'd like to start with a period of tests to determine how efficient it trully is for me. Does anyone have any idea how I should go about it? I don't even know where to start. Also, does it matter where I purchase from? I know that modup.net is the oldest and most established modafinil vendor, and the prices are fine too. Should I keep looking? For example, maybe I could find a cheaper option on Alibaba... Is there maybe a way to test the purity of the product fast? I have basic chemical equipment.