Well first let me say CONGRATS brother!!

MashAllah!!

Since you don't know her very well I would say something that would appeal to a lot of women. Maybe you could give her a sweet card and some roses or something??? You could give her some books on marriage and give her a card saying that you can't wait to go on this journey with her??

I can't think of any specific thing you could give her, but a nice card and roses would be nice? That way its not to over the top and your not giving her something she may not like.

Maybe someone else will come up with something better. I would say just use your imagination and get creative!!

Good luck brother!!
I wish you all the best!!