it's quite okay to invite for dvd night specifying it's just for nibbles. have individual plates ready with each containing appetizers like cheeses, a mixed salad, crackers and smoked fish. buy inexpensive but good drinking wine.

make sure they rsvp you so you know exactly how much food to prepare. and as it's a budget invite, every plateful of food is accounted for. you spend less than if it's a dinner invite.