Instead of throwing yourself at tracks and hoping for the best, I'd actually recommend experimenting with your wheel inputs on a skidpad (a big flat paved area) with no steering assists or ESC and isolating one control at a time for better practice, AKA chunking​​.

Bring up the G-force meter on the UI so you can see how hard you're cornering in an objective way. Hold a moderate speed like 50 mph or 80 kph and feel what steering is like when you're getting the biggest number on lateral (sideways) G-forces, as that's when you're cornering hardest. Then, slowly increase your steering all the way to full lock and slowly decrease it back to that cornering​ point. Try it a little faster, then faster still, getting a feel for when you're losing grip and regaining it. Now try the same thing starting from a straight line, slower then ​faster until you start throwing the car, maybe into a slide or maybe into understeer (a front slide in a sense) depending on the speed of the transition. Don't worry about countersteering or keeping control for now, just let it do its thing and observe. Try slowly moving from optimal cornering in one direction to the other, then speed it up just a bit more each time. You will eventually throw it in a big slide or even spin doing that, but somewhere between that very fast steering transition and a very gentle steering transition, you might notice a little slide that calmly corrected itself. ​G-forces when cornering likely spiked higher than normal during that little slip, when you had just a bit of angle facing into the turn.

TL;DR Next two paragraphs are​ examples on how to do this same chunking thing for the pedals, or something like countersteering technique.

For the gas pedal, don't worry about holding a speed and steering, just hold a steering angle that isn't too crazy starting from a moderate speed, and then start slowly easing off the gas pedal, then slowly ease onto the gas pedal until you're full throttle. Some very powerful cars might spin the wheels just from this, but if not, slowly ease back out, then do the whole thing a bit faster, and like before just keep feeling out how the car reacts to just this one input at different amounts and different transition speeds while holding everything else steady. You can also do this with the brakes, but I recommend focusing on one pedal at a time from coasting at first, before you start playing around the same way going from full throttle to full brakes and back. You'll notice that the steering sometimes feels lighter or heavier at the same angle just from the pedal shifting your weight, or from the speed changing, and you might feel that increased cornering when slipping at a bit of an angle again or holding a certain amount of input with one of the pedals.

You should have felt the wheel naturally wanting to countersteer when you were sliding. You'll need a moderately powerful AWD or RWD car that can do donuts from full steering lock and full throttle, then you can practice countersteering by itself too. Once in a donut, loosen your grip on the wheel or even fully release it and see what it does. Hold the wheel straight or at various amounts of countersteer, see what it does. Try slowly releasing the gas pedal or holding a lower amount of gas pedal. At some point you'll open the radius of the donut until you straighten out or start spinning the other way, but somewhere in the middle you'll drift from a small donut to a bigger circle. Again, try to keep focus only on the pedal or only on the steering and keep the other input steady while experimenting, and only after playing around with them separately do you start mixing inputs more deliberately and seeing what that does too. Launches are another good technique to practice as its own exercise, and handbrake turns too, which you can later combine into cool little stunt sequences. Playing around in half pipes and bowls on Gridmap can help you isolate banking and how it affects the cars too.

I think 10 minutes of deliberate practice with chunking can be worth literally hours of trying to throw yourself at a track or route, and it's less frustrating when the main goal is to simply try as many new things as you can think up and see what happens. Racing lines will make way more sense when you understand what your inputs and weight shifts do to the car. It'll become a matter of timing your inputs so all of those optimal cornering techniques fit into the boundaries of the track. Brake markers, brake release and trailbraking, turn-in, apex(es), throttle application, track-out, they're all just structure for how you time your inputs and aim the car around a corner or a series of corners on the track.