It does not lag with my PC, so I don't really see an issue there sorry ^^' If you got an old PC then it's understandable that it lags, or if you got an outdated video card or perhaps not much space on your computer. I'm not a specialist so I cannot for sure say what's causing this issue, but I know it's not from my side 
i put the dress on a dt base
What you put it on doesn't matter, because it is not an issue I'm experiencing. Check the physics on the model, and see if the physics overlap the dress physics. If it lags it lags, that's not something I can do.