Back in my day, a sweet thing was making a mixed cassette tape for your boyfriend/girlfriend. So, I guess that today's version would be a playlist of mp3's/m4a's. Pick a flower for her. Brush her hair in front of the TV. Give her a foot massage.
Be careful not to overdo it though: If you make tremendous efforts really early on, she'll be really disappointed when the infatuation wears off and you slow down on the romance. Make sure you keep it at a sustainable level.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.