I think you are wise, decent fabric would have cost a lot of money, and you wouldn't know how it turned out until it was finished. Sometimes fabric that looks great on the roll just doesn't live up to itself when made up, and eveningy type fabrics can be more 'challenging' to sew.
If you go on a dressmaking course you start off with really simple things, my mother would have fainted if a new student turned up and said 'I want to make a strapless evening gown'!
Hope you find something fantastic to wear.