Practice, Practice, Practice! That is what just about every article you read on how to improve your shooting will say. But how do you do that at 20 cents a round? There is no cheap surplus .ammo around anymore, so if you really want to punch paper or clang steel a lot you pretty much have to either be a trust fund baby, marry a trust fund baby, or find a way to shoot .22s. At pennies a round and available pretty much everywhere, there is no better tool for honing your shooting skills on the cheap than .22 Long Rifle ammo and a gun that shoots it well.
You can of course just go out and buy a regular garden variety .22, like a Ruger 10-22, Remington Nylon 66, Beretta NEOS, and numerous examples from Henry that are very affordable and shoot really well.
The problem with this approach however is that when you practice, most of what you are practicing is muscle memory and natural point of aim. Both of these will be different with a standard .22 than they will with your self defense or competition rifle. You can buy a gun that looks like yours, or even feels like yours, but there will be no substitute for being able to shoot your actual gun with .22 ammo.