What food do we start if a baby completes 3 months?

My child was not getting enough to eat, so at 6 weeks I started her on baby cereal. I would put about a tablespoon in her formula and feed it to her. She seemed to not have any problems and would sleep through the night. When she was 3 months old I gave her squash. It is recommended to start a baby off on lighter colors of food. Also "thin" cereal (oatmeal, rice cereals) is good for them.