I think it's ok to give your baby avocado if they did not have any reaction to cereal. I fed my son a bit of avocado last week after baby cereal for a couple of days. He didn't like avocado
Or you can skip baby cereal altogether and just other food like sweet potato, carrot, pumpkin, pear etc... because baby cereal can cause constipation in some babies. Like my son, didn't poo for 6 days after letting him try baby cereal...then he developed a rash. Wish I never gave it to him!