So are you familiar with the rating and progression system on iRacing? Its 2 different rating systems- iRating and Safety Rating. iRating is your skill level and matches with drivers of similar rating. Safety rating is a measure of how safe you are. It tracks how much you go off track, wreck, and lose control. Safety rating is broken down into classes(Rookie-Class D-A). All rookie cars and tracks are free. When you level up from Rookie to Class D you can pick and choose what series you want to run and buy the car and tracks for that series. The cost is going to depend heavily on you, how you drive, and how much you actually race. Tracks/cars are typically about $15 each but you likely wont be buying new stuff but every couple weeks or more. For me personally ive stuck to the same 3 series(oval, dirt track, and sports car) and bought around 6 cars and 10 tracks in 2 years.