think you can choose a gift based on his mother's condition and her personal preferences. You'd better choose a gift that will please her and is good for her health. When visiting a patient, generally speaking, fruits are a must. It's best to bring a bouquet of flowers. If his mother is hospitalized for a long time, you can bring some books she likes, or buy her a radio to relieve her boredom in the hospital.
In fact, gifts are just a form. As long as you are sincere, it's fine. You should visit her often, accompany her more, chat with her, etc., because there are many people in a ward. If everyone praises you, she will also have face, and naturally she will have a better impression of you.
In this way, I think the people in the ward will also say good things for you, hehe, so you can firmly tie the heart of your future mother-in-law. The above are my little suggestions, I hope it will be helpful to you.