Mothers can sense your feelings with your gift, so it doesn't matter how expensive the gift is, as long as it is from the heart.
However, it would be good if you could get an idea of her feelings too, and you can do that if you are a bit careful.
Look out for anything that she has plans to buy, and if you can afford it. For example, a dress, casual or just formal office wear. Or, it may be a hair clip with a touch of difference.
Check out if she is planning to get a new microwave, or that new steam iron, gift it to her if you can afford. But don't forget to add a personal touch like a perfume or a bouquet of flowers as an add on to those kinds of home durables.
Try to be guided by her likings. If she likes cats, how about gifting a pet or something that has a cat's impressions on them. But make sure she doesn't get to know that you're making a present. Just gift her as a pleasant surprise.
Definitely spend some time with her, especially if you are not staying with her. Make her feel special. Cook a special dish for the day, or handcraft a special greetings for the day.
You can also make a quite little party with special and closed ones for her.
And of-course, if she likes outings, make it with her. And if possible with your entire family. She loves it for sure. After all, she is the one who takes care of your entire family. A special show to the theater, or to the countryside, could fill her with the warmth of your care.