Workout/not lose weight tips

A

I’m currently trying to gain weight. Backstory I have an autoimmune disease and I lost 28 lbs and I’m trying to gain that back if not more, so far I’ve gained 15 back! I feel like most of it is my stomach, hips and butt. (I have a little bit of a muffin top) I want to gain it evenly so what are some good workouts that won’t make me lose weight but to tone myself and gain muscle mass?