There are a lot of past threads that deal exclusively with water storage. A general search should provide great kernels of information.

If your in an city area and your plan is for an extended stay at home without clean potable water I'd suggest investing in the 5 gallon water bottles and a spigot jug to sit on. If its to much to buy the bottles you can buy 5 or 6 gallon water carriers for about half price. I'd suggest 1 gallon per day per person. I usually keep 20 gallons for the three people in my house. Every six months I exchange the water in the carriers for use.

If your at home during or for an emergency, fill up your bath tubs with water right away. The water in the pipes won't be contaminated. One tub should provided at least 40 gallons of water that can be used for a number of other functions like flushing the toilet a couple times a day and hygiene.

For flavor, you can certainly invest in flavor packets. For true emergency, I keep powders like gatorade or kool aid or tea in large quantity. You don't need a whole single serving packet to mask the 'taste' of chemicals in water and it will stretch a long time.

I will hasten to add this and its not an admonishment, please don't take it as such. It's important to plan for emergency's and its great to plan for comfort but clean water in critical situations is a commodity and taste is a preference. If you have a choice to buy a $6 five gallon water container or $6 in flavored powder, buy the container.

BTW, if there is a Big Lots store near you, its a great place to find powdered drinks cheap.