What oatmeal is best to start my 6 month old son on?

I was going to avoid grains although and I am definitely skipping out on the rice cereal but he does need something a little bit sturdier to help with his sleep since he barely sleeps so I wanted to start with oatmeal. Can someone please let m know what the best oatmeal is to start on and how the best way to prepare and how much to serve a 6 month old who’s about 20 pounds

Edit: my son barely sleeps he needs something more filling. I didn’t ask what people opinion was on it I asked how to prepare it and what kind I should use. I get it’s a myth that it makes them sleep more but he needs something heavier to be able to sleep better. So please don’t criticize or say anything unless you are answering my question on which oatmeal is best