How long until I get the full effect of Adderall?

I have been taking Adderall for a couple of weeks. I notice that it has an immediate effect with focus/concentration/energy, but once the dose "wears off" I am back to my scattered/disorganized self. Will this medication "build up" in my system over time or will I just have to wait until the meds kick in every morning? I know anti-depressants take time to work, so I was wondering if I may need to take Adderall for awhile before I get the full effect?