For the current moment, the only racing drone I fly is the HappyModel Mobula 6. Although it is small it is quite agile and is very fun to fly indoors. Despite my relative lack of knowledge on the subject of racing drones, here is my mindset: To start out, get a small and relatively cheap drone and learn to fly on it. This has worked quite well for me so far and the other advantage of starting small is that it is not very likely to break and even id it does, repairs are not very expensive.