Start solids with rice cereal or oatmeal cereal?

Hello, my LO is approaching 6mo and will soon start solids. Have always been fully breastfed, hence unds there's a need to start with iron-fortified rice cereals. Because of the high arsenic level in rice, may I check if I can use the alternative oatmeal cereal instead? Read that gerber has iron-fortified oatmeal cereal as well. Does it matter to introduce rice or oatmeal cereal? Must I eventually still try out rice cereal since rice is like our staple food? #firsttimemom #pleasehelp #advicepls