Experiments find long-term happiness and satisfaction come not from what we have but what we do. It seems experiences mean more to us than things do.
I think this is especially true for couples – money spend doing things with her will satisfy her more than buying her stuff. Based on that, I suggest a majority of the money you spend “on her” should go towards dinners, movies, going dancing, museums, day trips, vacations, and so on.
If money is tight, look for ways to “buy” experiences on the cheap. Make a picnic meal and take a drive to the beach, the mountains, a national park, or some such. Find a way to go to movies when the prices are lower. Look for deals on off days and at non-peak times.
If you are not struggling financially there are great deals from vacation locations hurting for income. Maybe it is time for the vacation you have always dreamed about.