Everyone wants the 500-horsepower answer. But a car that's easy to go fast in is a car that hides your mistakes — and hidden mistakes don't get fixed.
A slow car forces you to carry speed, to be smooth, to think about the whole corner instead of just the exit. You learn car control at 70 mph instead of scaring yourself at 130.
Buy the cheap, honest car. Spend the savings on track days, tires, and an instructor. You'll pass the fast cars soon enough — and you'll actually know why.