The wrong first car is frustrating. Tell me how you like to drive — I will recommend the most predictable GT3 and where you should learn it.
Not every GT3 is equally beginner-friendly. The most forgiving cars are already in the base game: BMW M4 GT3 (stable, the top pick), Aston Martin V8 Vantage GT3 (neutral, excellent brakes), McLaren 720S GT3 Evo (lots of downforce, predictable) and Audi R8 LMS Evo. The current meta favorite, the Ferrari 296 GT3, is just as approachable but belongs to the DLC.
What to avoid at the start are the rear-engined Porsches (911 GT3 R, 992 and 991 II — lift-off oversteer) as well as the oversteer-happy Lamborghini Huracán GT3 EVO2 and the old Aston Martin V12 Vantage GT3. Good tracks to learn on have wide run-off areas: Monza, Misano, Paul Ricard, Barcelona and Silverstone. Bathurst, Zandvoort, Brands Hatch and the Nordschleife have walls close to the track and only make sense later.
The BMW M4 GT3 counts as one of the most stable and most predictable cars, closely followed by the Ferrari 296 GT3 and the Aston Martin V8 Vantage GT3. All three forgive mistakes and have strong brakes.
The rear-engined Porsches (911 GT3 R, 992 and 991 II) because of lift-off oversteer, the oversteer-happy Lamborghini Huracán GT3 EVO2 and the old Aston Martin V12 Vantage GT3 — they are nervous or oversteer-happy and punish mistakes early.
GT4 is an even gentler entry: around 7–9 seconds a lap slower, less downforce, a simpler setup and more forgiving. A few hours of GT4 before GT3 is a very sensible ramp. GT2, on the other hand, is not a beginner class.