With the cost of ammunition right now, it's amazing anyone can afford to practice without getting some good coaching first to be sure they're practicing the right things.
According to Schmidt in Motor Learning and Performance, it takes roughly 300 to 500 repetitions to ingrain a motor program to the point you no longer need to think your way through it every time you do it. However, to erase a previously-learned program and replace it with a new one takes 3000 to 5000 reps -- literally ten times as much work!
Also, that second number goes up dramatically when the earlier program has been "overlearned," that is, when it has been trained to the point of true automaticity. The rule is, the more thoroughly you have learned the first program, the more work you have to do to erase that old program and get yourself up to speed with a new one.
Of course you can teach yourself to shoot. Here's the math on that: you first spend a couple hundred rounds figuring out how to do the skill. You will hit on a way to do it, but probably won't find the most efficient, safest, best way to do it. You'll find something though; it will be an improvement over what you were doing before. So you have something that works, and you practice that.
You keep practicing that workable-but-not-best method, say for another thousand rounds. That's a year of shooting for most people. Most of us on TFL are shooting more than that, and some of us are shooting a whole lot more than that. If you do any dry fire, you can probably multiply those numbers by a factor of ten.
That means that when you finally do get into a class or hire a coach, you'll find two things:
1) There's almost certainly an easier, more efficient, better way to do the things you want to do, and
2) The brand-new shooter standing next to you will spend a whole lot less ammunition learning them.
My personal website: Cornered Cat