You can never blend in in Egypt. Egyptians wear normal clothes nowadays and no one wears the native clothing which is like long dress (except old people in small villages) and I am sure you do not mean the very old native clothing of Egypt or you would look like a Pharaoh which is not blending in :) and not to forget that you are Caucasian which is hard to change to look like Egyptians...
Furthermore, Egyptians are born with the ability to know foreigners, I am an Arab who looks like any Egyptian and wears the same clothes and they still spot me and know that I am a foreigner.
In addition to that, from your description of yourself and as Rory has commented, it will be hard for you to blend in easily.
My advice to you, wear whatever clothes you wear at home (unless you are from an African tribe that wears nothing) and act normal and you will be just fine. Also, try not wear anything that shows your tattoos in Egypt, tattoos are for criminals in Egypt so showing them means you are either a criminal or a foreigner.