ETA: shouldn’t use normally edible parts to make stock. Only like the tips and tails of carrots, celery root balls, onion peels… I keep a gallon ziplock in the freezer that accumulates these as I cook other things. When it’s full I usually make chicken stock.
I cook for a 5 persons household, and I fill 4 to 5 1L Ziplock bags with vegetable peels, tips/tails and other "garbage", which I then turn into 1 to 2L of stock. We also eat a lot of pasta, and I make sure to keep the "skin" of parmeggiano or grana padano we eat, and throw it in there as well.
If you try it, you will likely be surprised by how mich usually gets thrown away.
Nope I just use whatever is in the bag, I don’t care too much about the ratio. But we try to eat lots of carrot/celery sticks for snacks, and I regularly cook things with mirepoix so there’s not exactly a dearth of them.
You can also "splurge" and make a veggie stock using whole ingredients; for example, I use whole fresh celery, carrots, peppers, onions, and garlic. It's like $5 of ingredients.
ETA: shouldn’t use normally edible parts to make stock. Only like the tips and tails of carrots, celery root balls, onion peels… I keep a gallon ziplock in the freezer that accumulates these as I cook other things. When it’s full I usually make chicken stock.