Nobody can say with absolute certainty whether or not they’ve seen Luna truly drunk. It’s definitely the case that if Harry drinks something Luna has mixed, he is basically already asleep on someone’s lap (Ron’s? Ginny’s? Neville’s? Who can say!) but Harry is a notorious lightweight.
Drunk Hermione will explain at length that she is, in fact, drunk.
Getting Ron truly drunk is also pretty challenging, because he’s like nine feet tall with a fast metabolism and eats while he’s drinking. If you can manage it, he just falls asleep, and then is irritatingly chipper the next morning.
Drunk Ginny is a lot of fun, especially if your idea of fun includes flashing the entire dance floor and trying to get your friends to hook up. (Listen, okay? I’m just saying. I’m just saying Dean and Seamus are perfect for each other, all right? They should snog.) Just don’t make her mad, because she will fight you.