Starting cereals and purée baby food

I have a 4 month old and his pediatrician said it would be okay for us to start baby Cereal mixed with formula. I started giving him baby oatmeal cereal mixed with his baby formula and he takes a few baby spoons here and there but doesn’t seem to enjoy it much. Still mainly having formula in the bottle. His pediatrician is not very strict in terms of how to begin giving him cereals and purées she just gave my husband and I general idea of where to begin and try it. Wondering other moms opinions? Recommendations to begin giving baby cereals? How long does it take for the baby to really take to the idea of cereals and purées? Anyone have any good recipes for baby purées or cereals? Any brands they enjoyed ? Any recommendations would be greatly appreciated!