Did the doctor explain why your baby needs solids this early? Did she say you HAVE to start now? At 4 months, breastmil k still provides all she needs, and there is no benefit to replacing it with solids.
If you are determined to start now, probably better to offer fruits or veggies. They have more flavor. Cereal, whether rice or oats, tastes mostly like the milk it's mixed with. A few bites of applesauce or green beans or avocado, once a day, after her regular breast or bottle, is ample.