First time experience, but, what do I wear to a banquet?

Sorry if I’m oblivious, but I’m a trans girl (17), and I have a banquet where I intend on going to but feminine/feminine presenting for the first time. Could you ladies (and ofc anyone with experience as well! :D) point me in the right direction? I’ve been told cocktail dresses and what not, but if so, I’m kinda on a budget of your average broke teen girl 😭 and I have to buy discretely overall. Kind of an overloaded question, but where is a good place to shop? Love y’all!!