Like ilene said, you really shouldn't run every day. Running is really hard on your joints and they need recovery time. Your instinct to take a day off in between running days is a good one.
Walking can be done every day though
. However, it still a good idea to switch things up so you aren't sticking to one activity. Muscle confusion and diversifying exercise is what helps keep the heart and muscles strong and not get too "comfortable" in one routine.
Yoga, elliptical, biking, and swimming are great non-running day activities.
Lifting is super important for a lot of reasons so definitely consider starting to incorporate that into your routine