OK, pills, even when tested, you'll enver be sure of exactly whats in them. A good mdma+chargy pill is quite often a good dose of mdma with a small dose of some kind of amphetamine.
Pure mdma, while different from person to person, can basically break down like this IMO
light dose: A small dose will leave you feeling warm and fuzzy, slight waves of euphoria through your body. Some people might get energized by it, feel like dancing, chatting, etc.
medium dose: A medium dose will leave you extremely euphoric, nice waves of euphoria with a possible strong peak of constant euphoria. This will make many people feel *chargy*, like dancing, chatting, etc. The more often you use, the less energy you will get though. This is your cliche mdma experience. You may also feel very horny.
Strong dose: A strong dose of mdma is unlikely to leave you feeling like dancing. Visually things are getting pretty weird. Your eyes are probably rolling back into your head. Lots of jaw clenching, etc. Your too fucked to move during the peak of this. Even talking is difficult, though you will babble crap to anyone who sits near you. You'll be very horny, and having sex in a night club toilet will start to look like a damn fine idea, though you may not function correctly. Your body is almost in constant orgasm from the euphoria at this point. THings like blow-up tricks etc will also be grand at this point of experience. This is a heavy dose, better suited to house parties than clubs, since it really will put you on your ass. A line of amphetamine however, could quite easily make you feel like the dancing king, but will result in a far harsher come down. Pure mdma comedowns are generally known to be fine, cept that you may really be dissapointed that the drug has worn off.