This is a very difficult endeavor for you but I asked my mom to leave her granddaughter videos of herself talking about her, the things she likes to do, her views on life and anything she wanted to tell her.
The most important thing was that she did this early on because your energy goes away. The videos need to be done NOW. The letters and writings can be done right up until about a week before the end.
Tell her about your childhood
Tell her about your first love
Tell her about your first kiss
Tell her about what you thought when she came into this world
Tell her about when you found out your wife was pregnant
Tell her about everything you have any emotional connection to.
Tell her your hopes and dreams (not of her, but yours)
Tell her how much you love her and give her confidence.
Tell her how you want her to make an impact on the world for the better no matter how small
Tell her whatever is on your mind as you write.
The most important thing is to give her things to remember you from. A nice touch is to create a letter or video for each birthday, but keep in mind she won't be able to handle these until she's much older.