Enroll in Decluttering Simplified
The whole point of decluttering is to have enough, but not too much. 
It's why I won't ever give a list of what you should have, or how much. It's different for everyone, and it changes based on your season of life, home size, and more. 
The only way you will figure out what this balance is for you is to actually declutter! Dive in and get started with Decluttering Simplified. It requires action, and introspection. Asking yourself questions and thinking critically about what you have, need, and use. 
How do you tell if you have enough, but not too much. 
Toys
Clothes
Dishes
Parkinson's law says if you have more, you're going to use more and then you get stuck in this cycle of being too far behind to actually catch up.