100mg in the morning although some of my friends take 200mg. 100mg is enough for me to keep me awake/motivated/focused to about 4-5pm; rest of the day is ok as well and I usually sleep very well after that (interestingly I need less hours of sleep having taken modafinil in the morning). Depending on country you can get it from various sources in some (UK for example) you can just order it from India 100% legally. In US it's more of a problem but people still get it. Try reddit/r/nootropics for a start (and recommended places to get it). I also like /r/ADHD for community/support. Please consider what I wrote as personal very subjective testimonal and in no way an advice, let alone medical. If you decide to take any drugs please at least read about possible negative effects/precautions you should take.