Gender reveal parties aren't typically gift giving events, but if you don't want to show up empty handed I would keep it small. A onsie, a card or maybe some flowers. If you are close to the couple you could do a card with a gift card inside.
I don't think they are gift-giving events, but I never show up at someone's house empty-handed, so I would take something - a book for the baby, or flowers for the parents.
Re: What to bring to a gender reveal party?
Created by MyFitnessPal - Free Calorie Counter
TTC Since January 2011 - We have bad spermTTC since 1/13 DX:PCOS 5/13 (long, anovulatory cycles)

Clomid 50mg 9/13 = BFP! EDD 6/7/14 M/C 5w6d Found 11/4/13
1/14 PCOS / Gluten Free Diet to hopefully regulate my system.
Chemical Pregnancy 03/14
Surprise BFP 6/14, Beta #1: 126 Beta #2: 340 Stick baby, stick! EDD 2/17/15
Riley Elaine born 2/16/15
TTC 2.0 6/15
Chemical Pregnancy 9/15
Chemical Pregnancy 6/16
BFP 9/16 EDD 6/3/17
Beta #1: 145 Beta #2: 376 Beta #3: 2,225 Beta #4: 4,548
www.5yearstonever.blogspot.com