Baby cereal question

Thinking of starting my little one 4 months, on baby cereal but not sure if he’s all the way ready or if I’M all the way ready. He gets only breastmilk through bottles.

I’m wondering if I give him a couple bites of the cereal do I have to continue to give him cereal everyday?

If I give it to him once and he or I am not ready and want to wait until he’s 5-6 months can I do that?