According to my siddur (p. 231 of The Complete Artscroll Siddur), one makes a shehechyanu upon buying new clothes, and a malbish arumim upon putting them on once acquired. (I have heard from other sources that shehechyanu is made upon putting them on.)
But how would one make any bracha during or immediately after putting on clothes that require a full change? Is the procedure to make the bracha before putting on the clothes, or does one put on the clothes, ritually wash the hands, and then make the bracha?