If it is high purity meth, 100mg will be a pretty strong dose, don't expect to sleep within 12 hours of taking it. Could very well keep you up for 24 hours. Then again if you take 3 pressed pills of MDMA perhaps it won't seem that strong, but who knows. Meth lasts a long time.
Also, meth doesn't work as synergistically with alcohol as cocaine does, in fact meth seems to reduce desire/appetite for alcohol to a degree. Experiencing a hangover while the meth is still wearing off isn't fun either.
Don't know about using it for dancing and raves, that was never my thing, but it will definitely keep you up. Never mixed it with MDMA, but have heard of some people having success mixing low doses of meth with MDMA, seems like you'd want to take the meth after the MDMA is wearing off though as to not dirty the effect of the MDMA, not sure.
Becareful!