Honestly? I don't think you need to give her anything, at least not of material value.
If you're going out somewhere, just pay attention to her cues. You may have the opportunity to spontaneously pick something up and present it to her on the spur of the moment. Otherwise, I think you run the risk of being seen as old fashioned or as trying too hard.
Really, I think your best bet is to do as Equus suggests.
Be open, be honest and be yourself. Hopefully, she's going out with you because she likes you and she wants to get to know you better, not run your name through Dun & Bradstreet so she can evaluate your gift-giving abilities.
