I take Vyvanse and its good. It helps me concentrate a lot. But if I don't take it I feel high as fuck and can't do anything.
I wouldn't advise taking more than one a day because you won't be able to sleep and that would be considered overdosing.
It is really easy to get a prescription. Just tell your mom you think you have ADD/ADHD and she can take you to the doctors. They will easily give it to you.