A cruising budget is easy to establish.
It's $300 in January - still got lots of stuff left after Xmas
It's $55 in February, that's how much fuel it took for the month's sailing to and around that island group.
It's $3000 in March - the supermarkets and diesel are really inexpensive here so we've stocked up on all our supplies.
It's $0 in April - see March above.
It's $350 in May - see March above and wife's birthday with a dinner on the town + gift.
It's $3800 in June - the genoa started falling apart, needed replacing
July, August, September - $0 - spent the time lazing around the Tuamotus fishing, diving, swimming, reading, baking, a little fixing, doing the things that cruisers do.
Oh, you're looking for an average? Sorry, can't help you there.