I was so fortunate to be able to reuse my Mother's wedding dress. We just so happened to be getting married the same year as my parents 30th wedding anniversary and my grandparents 60th, so using my mothers dress carried even more sentimental value.
I reused everything-except for the satin bows on her puff sleeves.
I did buy new satin for my dress because I wanted it to be matte, but I still used her skirt as underlining. I did have to build myself a corset and buy buttons. All in I spent about $100 on my wedding dress-and countless hours.
I made my own pattern so I had to experiment a lot with muslin. And I have to tell you it is impossible to give yourself a proper fitting!
I am currently doing alterations for another bride.