The price and style of the clothing:
One should not wear expensive clothing as this brings a person to haughtiness. Nevertheless one is also not to wear very cheap [low class] clothing in order so he is not disparaged in the eyes of others. Rather one should wear average priced [middle class] clothing.
Buying expensive clothing for one’s wife:
Although the Arizal did not wear expensive or overly extravagant clothing nevertheless regarding his wife he was very careful to purchase for her even very extravagant clothing. He would fulfill her wishes even if he could not afford it.
 Kitzur Shulchan Aruch 3, brought in Ketzos Hashulchan 3/3
 Shaar Hamitzvos Parshas Eikev, brought in Kaf Hachaim 2/22