I have already got diapers, Sonic bedding, plushies, any recommendations for me to complete my inner baby?
Everyone is different on their likes and interests when it comes to ABDL stuff. Some will feel little with a bottle, and others don't want any part of a bottle and prefer cups or sippy cups. You might take a walk down the baby / toddler isle in the store and see if anything pops out at you, that gets your attention.
I've got onesies, bottles, sippy cups, sleepers, plastic pants, pacifiers, etc. For me I don't really care for much of it, and don't really use any of it. The exception is sleepers. I always feel really happy when the weather gets cold enough that I can start to wear a sleeper again at night. Pacifiers are another thing that I like too. I sucked my thumb for almost all of my life. So using a pacifier is comforting to me.
Find things that you like and draw your interest.