It's always more important to be slightly overdressed than underdressed. Last Saturday I attended my cousin's engagement party. The invitation contained no dress requirements, but of course I wasn't expecting a casual affair. The invite did, however, mention dancing and an evening start time.
My point is this. Style isn't about simply looking good. Style is about feeling good while looking good. Engagement parties can be awkward enough when you're among the next in line to get married. Functionality in one's wardrobe will always allow personality to take the forefront over the look of one's outfit. Therefore, I came to the party in very comfortable yet stylish brogues and a pima cotton sweater, instead of a merino wool one.
The shots will get better - more clothing, less me. The whole look cost under $100. Thanks to thrift shops and taste among other things, style is never about money.