The secret to buying Oilily clothing that fits is in making sure that you pay careful attention not only to the general sizing chart, but also the actual measurements given by the seller.  If the seller does not provide measurements, make sure to ask for them prior to bidding.

With new clothing, measurements will help you determine whether an item will fit you.  There are some Oilily items (primarily blouses) that, although they may say a size 44, for example, are cut on the smaller side and cannot be worn by a woman who is a regular size 44. 

Used Oilily clothing is a bit trickier than brand new clothing.  If the clothing has been washed even once, it will have shrunk to some degree (I've seen as much as 2 inches after one hand wash).  Even if a person has washed the item by hand every time, there will still be some shrinkage.

The nice thing about Oilily clothing is that it is well made and will last you for a long time, so take good care of it.  Hand washing for most Oilily items will help them retain their vibrant colors longer, machine washing strips them faster.