The supermarket has what you want. It's what I do.
1 gallon jugs; clean, pure, safe, sealed.
Store on metal shelving or other strong stuff; water is heavy!
I've never had a problem with leaks, despite my gallon jugs being a decade old. Maybe they'll all go at once, I don't know.
The key is to set up your storage so it's cool, dry, airy, and in the dark. Everything lasts longer. Then leave them alone, unless you use them. Don't be playing musical jugs because that will lead to leaks.

I tried repurposing recycled containers (like 2 liter soda bottles) but the cleaning and the bleach you have to add to keep the water pure was more costly in terms of time, money, and stability than just buying the gallon jugs at Walmart.

If you feel uncomfortable about storing store-bought jugs of water for decades, then buy them and use them, renewing your storage regularly.

Don't forget you've got emergency storage possibilities if you've some advance warning: fill every jug and container in your house (particularly those very nice 5 gallon water coolers they use on construction sites) and your bathtub (for flushing toilets).

The best way to store water for your garden is in the ground. Improve your soil (this will take years) and your soil will do much of the work for you. Rainbarrels and cubes help a lot, but only if you use them. Installing a cistern and a pump puts you in the big leagues. Can you drill a well?

Know how to minimize water use with disposable plates, paper napkins, and plastic utensils. Sponge baths for you with a washcloth.

You may want to look into buying a Big Berky, to purify water. There are other methods too. At a minimum, let your salvaged water from the creek stand and settle, pour off the clear water, stand, settle, repeat as needed until it's as clear as you can get it, and then boil what you have left.

Hey! I wrote a book on the subject, covering much of this in detail: https://peschelpress.com/fed-safe-and-sheltered/

There are plastic jerry cans. I don't really even know where to get a metal one anymore. The plastic would be of the same type plastic that many people buy consumable liquids in already.

We have a variety of water vessels. Our collection is based on needing to really economize, so there is a lot of re-use. I recommend you look at every vessel that comes into your possession and ask whether you'd be happy to drink from it if you were desperate. Small containers may not give you that feelingof being all stocked up, but you can put away a lot of them in small places, making for a good stock overall.

I started with empty bleach, vinegar, and milk jugs, intentionally buying those products in the largest bottles so that I could re-use them for water. (I once had four gallons of store bought water in gallon jugs. Both the milk jugs and purchased water jugs eventually leaked at the seams.) Next, I started keeping water in 2L soda bottles and glass wine bottles. We did buy the wine, but others were accustomed to saving soda bottles for us for garden use, so we get plenty. Then I even began to use some quart bottles that isoproplyl alcohol had been in. Finally, we have added some 7 gallon purchased containers for about US$25.

We do have a couple 17 gallon barrels that I keep thinking I should fill even though I'm not happy with how well they seal. These were shipping containers for encapsulated psychiatric drugs (!) so some might raise an eyebrow, but we already used them once for fermenting, so obviously I'm okay with it. Not all needed water is needed for consumption anyway...

Here is why I know that I need water stored. This photo is from earlier this year, just two houses away from me. A water main had leaked undetected long enough that it washed out a cavern under the street until there was no longer soil supporting the pipe though about a 14 foot distance. The pipe broke and gushed so strongly that geysers popped up in the street in multiple places. Infrastructure is failing left and right.

How about glass sun tea jars? Or gallon glass pickle jars? You'd have to clean them well but they're glass and should come with lids. They're not hard to find at thrift shops.

As always, you'll need heavy-duty shelves to support all that weight. You also don't want to move them or jostle them. A leaking plastic gallon jug is annoying. A broken glass gallon jug is a hazard.

Great thread, thanks for the link! When I get a place of my own, I'll probably go back to a similar idea with cistern buffers, regardless of the main water source.

Yes! "Canning" your own water for storage is a thing that is done. I would still be cautious about storing them in full sunlight, but it is indeed entirely possible. I believe sailors in the 60's and early 70's would take tinned water in metal cans with them as backups, in case catchment failed or their storage tanks sprang a leak or took on saltwater somehow.

You could freeze some extra water (with plenty of headspace!).

You'd fill up empty parts of your freezer, keeping the electrical load down if the freezer isn't full to the brim.
When you need to free up some space, it's just water. Go ahead and drink it.

If you lose power, the frozen canning jars of water will keep everything else cold.

A jar of frozen water is a tell-tale for power outages: fill the jar halfway and freeze. lay on a quarter or a shiny dark marble. Add more water and freeze. If the marble's at the bottom of the jar at a later date, you know you lost power.

You can't store a lot of water this way, but you've got some and more importantly, you've got blocks of ice to keep coolers cold.

As I see it, the only resource that would be used would be the fuel to fire the canning kettle. Reusing canning lids gives you more use from an increasingly expensive item. You could certainly use the collected water from waiting for the hot water to arrive to fill the jars. However, it does take time to run a load through the canning kettle and I suppose our time is a resource that needs to be conserved and respected.