I don't know the etiquette of this, but just wanted to share a funny story. I had never heard of an engagement party before either, but my best friend's friend had one. She got 2 champagne glasses as a gift that were supposed to be used for the wedding toast. Not even kidding, 1 of them broke THAT NIGHT and then the other one broke the next week and they ended up not getting married!! Talk about a sign! LOL.
p.s. I totally cannot remember if I got her a gift but I'm leaning towards no, I didn't.