Cheapest stuff you can shoot, or I should say might be able to shoot as it's dependent on what your individual gun can shoot, is .32 ACP. If your revolver can shoot .32 ACP, great, but even if it does, accuracy isn't a guarantee.
.32 S&W Long from either Magtech or PPU is the next cheapest ammo to shoot. It's built for revolvers, the results are a known quantity, you don't have to wonder if they'll go bang like .32 ACP may or may not.
One issue that you will likely find if you use lead bullets, which is what .32 S&W Long is generally loaded with, is those bullets are usually measuring .311-.3125" and the throats for the .327 revolvers Ruger makes are usually .313-.314", which means you will get leading in the bore because of hot gases blowing by and softening the bullet, which gets stripped off as it goes down the bore. This can also lead to bad accuracy even in a clean bore as the bullets don't seal the throat as they move into the forcing cone and that causes inconsistent powder burn from shot to shot.
Ruger makes their .327 revolvers in a way that they expect owners will only shoot .327 in the guns and because of the high velocity, jacketed bullets are mostly used. It really hurts the utility of a .327 revolver and it's a large reason that I've been turned off of the cartridge in recent months.
Don't bother looking for .32 H&R Mag, that stuff is even more expensive than Federal .327 American Eagle and harder to find too.
Now, when it comes to defense ammo, you're down to a few options. .32 ACP and S&W Long are non-starters, they're too weak to bother spending your money on when you can get more powerful H&R Mag and .327 Mag instead.
Hornady makes an affordable .32 H&R Mag load that I've not seen tested, but it's Critical Defense line and that stuff generally works well. It's loaded more on the moderate side, but Buffalo Bore is another option and they make the most powerful .32 H&R ammo on the market. They call it a +P load, but it's basically a max load .32 H&R that they say shouldn't be used in any of the original H&R manufactured revolvers from the 80s.
There's not much for .327 defense ammo, there is one Federal JHP I know of, Speer use to make some .327, but idk if they still do, Buffalo Bore does and if you want the hottest of defense ammo, they're it. Personally, with the .32 H&R load they make, I don't see the need to go with the .327 at all, especially if this is a gun for the wife. If she can't take much recoil, get the Hornady Critical Defense instead.
