Definitely, the first dress and here is why: 1. The first dress is a bit racy and that's good for a first date. 2. The second dress is too conservative. Elementary school reachers were dresses like that. 3. The third dress is nice, but that's the sort of dress that is less racy than Dress 1 but also makes a good dress for formal functions like the company annual Christmas dinner.
Dress 2, pair it with a white shrug cardigan. The other two I think aren't good for a first date, they're nice, but it kind of says you're trying too much. Dress 2 is fun and flirty while still being just casual enough.
I hesitated between the first and the last one, ended up voting for option C, because; 1) the blue one might be too revealing and you might not want to send a certain kind of idea to the guy in a first date. And 2) I don't know what your skin/hair color is and so I'm not sure how that blue would look on you, Black suits almost everyone. But both dresses are pretty