I would focus on getting your nutritional status up prior to surgery, it is very difficult to get weight up prior to surgery. If you can eat a protein with a carb, a vegetable with a carb, a fruit with a carb. If you can supplement with boost or another nutritional drink do so. Surgery takes a lot of you and you will not be able to eat normally immediately after the surgery. I does take time for your body to get use to eating again. A multivitamin if you can tolerate one is not a bad idea, all my supplements are in Gummy form as I seemed to tolerate those best. When is your surgery scheduled and what type of surgery will you be having done? Have some more advice as you go through this process 😀 however I don't want to overwhelm you with information.