How much money should I give to an acquaintance getting married?

She’s more so an acquaintance and when our mutual friend is in town we hang out, that’s the only time. She’s getting married and my friend was invited along with her husband. He couldn’t make it so the acquaintance said I can come along or one of her other friends.

My friend asked me to come. It’s soo last minute but at a delicious steakhouse! I was thinking maybe $25–30 for someone I don’t know? Would that make me look cheap? I wasn’t even invited originally.