For the health benefits of onion it's recommended to eat at least one medium sized onion per day.
You can chop up the medium sized onion and when you get a cup full of the medium sized onion then you're eating the correct serving of the onion per day to get the health benefits.
I like onions but I cannot eat them everyday because if I do I get a stomach ache and have too much gas in my stomach which makes me burp too much or have acid in my stomach come up at night.
So you may not be able to eat onions everyday and that's okay as well.
You can still get the health benefits from onions when eating a few onions per week even when you're just adding them to hamburgers, stews etc.
Raw onions are healthier for you though than cooked onions though so yes eating raw onions even a little bit of of chopped up raw onions per day is good enough.
Eating raw onions helps the body create new cells due to the raw onions containing fiber and folic acid, and B vitamins.
The raw onions can help regulate blood pressure as well and detox your body and improve your energy levels as well.