Strangely enough D5 are not blank white pills. You wont get done for possion or intent to sell MDMA.
Theres alot of good input so far.
ive always had 5 at once, and like FRY-d said, the first time i had them that was too much. If you start low and dont go overboard, you can lower your resistance.
I have a friend who goes to the same clubs as me for longer then me, and she gets the same effects off 3 d5 as opposed to my 5 d5, because shes never had to increase her dose.
dextro does keep you up for very long periods of time too, so i recomend taking them earlier in the night... obvioulsy if you have 10 you wont sleep for a long time, but 3/4/5, you can sleep around 6 or 7 (when you get home)
My advice (much like the other smart people here) is to find your niche, see what feels good for you.
Remeber. You can always take more, you can never take less.