The answer is it's up to you and how intense you want/need the broth to be.
Now here's my lazy person's version (not recommending this to you just passing it on)
plus I juice fast so I'm so loaded with minerals that the broth is more a pleasant hot drink for me and a nice way to get my kelp, dulse etc. I find this broth has saved me many times! Easy to take in the car, to work etc.
In a pot w/3 quarts
distilled water (no stainless steel etc.)
3 lg organic russet/idaho potatoes
big handful or two of greens
peel big handful of carrots
lots of garlic etc.
half a handful of assorted kelp, akambi etc. to get sea minerals...
NOTE: I now only buy organic kelps...no more natural stuff out of the ocean
sad but true
Then I add onion whatever is left in the frig...
Simmer for 20 minutes (figure the potatoe can't cook and won't get too much starch).