IMHO, 1000 rounds for each gun you own.
In addition, a minimum of 2500 rounds for your SHTF guns. I keep a large stock of 9MM, 5.56X45 and 7.62X51.
An unopened case of 5000 .22LR is a good idea. It's always a good trade item as well as a practical item.
For those who have fought for it, freedom has a taste the protected will never know!
Or at least they did before political correctness