I usually shoot a few rounds a week, shooting is like riding a bicycle, once you get proficient, at least for me I stay proficient. Yesterday I was showing a neighbor my 32-20 police positive, and put a few rounds in a brick at 30 yards. I tend not to worry about COM training, I learned a long time ago how to hit a rabbit with a 1849 Colt pocket pistol. If you can hit a rabbit or squirrel with a pistol, you can easily hit COM on a human. Just pretend the target is holding a rabbit COM. My targets for pistol shooting have always been small, tin cans, bottles, bricks.
Now that 22LR is available, shooting it is a good way to save money and increase skill. That same neighbor was asking me about buying a rifle for plinking and was shocked at the prices of center-fire rifles. I told him if his only use was plinking, get a 22. They allow a person to learn the basics without fighting recoil, noise, and muzzle flash.
I still shoot with a 22 revolver and rifle, pellet rifle, and airsoft pistol. No need for silencers 22 rifles are quiet, airsoft and pellet guns make virtually no noise. And for city folks save going to a range to shoot. For me the main reason for shooting center-fire is making sure that my firearms function, or are broke in. Once that happens they may sit in the safe for years. I am not any better shot than anybody else can be, but shooting thousands of rounds will not make you a great shooter. Practicing the basics will, and that can be done with dry firing or any other inexpensive method. I worked along side police officers who fired the same amount of rounds I did or more, and still could not hit the broad side of a barn.
Practice your grip first, this is the most important part of shooting, a gun should be just like pointing a finger, or even throwing a baseball. Proper grip will put it on target with less effort. Proper form is the next thing that is important, learn to shoot correctly from different positions. Trigger control and sight picture come hand in hand, and can be accomplished with dry firing or a airsoft pistol.
Ammo properly stored will last for centuries, there is no need to shoot it up and replace it with fresh ammo. Back when I got my first 1911, around 1979 I bought a case of WWII ammo. That ammo was over 35 years old and functioned just like new ammo, and it probably saw some moisture at some point in time. I have washed accidentally ammo in the washing machine, then loaded it in a gun and it fired just fine.
As I said before, buy as much ammo as you want, shoot it as much as you want, it is a personal choice. You can never have too much, but you can have not enough. Just know that if the your bank account is not up to shooting thousands of rounds to be effective, you do not need to.