An honest supply is what you will really need based on what you really use now. 

 Remember you use way more than that to bath, wash clothes, and even cook many foods that require water. (Pasta – beans etc).

 You may want to keep in mind that water is heavy and can not be compressed to save space so storage of 100 gallons takes up a large space. 

 So with the above in-mind let us say you are planning on a 30 day supply of water for a family of 4, two adults and two children.  Well for drinking water that's 4gallons x 30 days = 120 gallons or 24 five gal. Water cooler type bottles, or two 55 gal. Drums plus 4 water cooler type bottles.  You can see that this will take some time and planning.   And that is only for drinking no baths, no clothes washed, no dishes cleaned and so on...

 This is where the honesty part is played out.  You can buy a case of water from a club store and have 2 or 3 water cooler bottles around and call it your 30 day contingency plan, but your only fooling yourself and setting things up for a really rough time if you and your family really need that water.

 So right off the bat you now might be saying “man this is tough” or “wow, more work than I imagined”.  Yes and an emphatic NO.  Yes it's work but your life and family is worth a little time and effort.  You start a journey with planning and one step at a time. 

 YOU THINK IN TERMS OF SYSTEMS NOT ITEMS

 So you know you need 120 gallons for your family to drink for 30 days and hygiene is both important and desirable.  So you buy a supply of plastic forks and spoons with a supply of paper plates and cups.

 That way you need no extra water for dish washing.  You stock up on hand cleaner, the kind you pump on your hands and don't rinse off.  Keep rain barrels that collect the rain run off your roof to use for flushing your toilette, washing your clothes and bathing.  And last but not least buy a quality water filter. One that is gravity operated like the British Berkey filter.  In-fact buy 2 with spare filters.

 That way if you have a source of water but the drinking quality is in question you can  filter it to drink and keep your bottled water in reserve to extend your self sufficiency.

 Now that is a system.  You buy what you need from a list you make when Items go on sale, or buy a few things at a time as funds permit.   Remember dollar stores sell most of this stuff so crying poverty is only an excuse.  You are in-charge of your life, make it happen find a way!