The finale is actually a showcase in this game, but even after that, there is no real “ending” per say. However, if you’re looking for a race to end all races, I would suggest running “Goliath”. It unlocks at Byron Bay level 4 or 5, and it is 4x longer than any other race on the map. It also pays out much better over time than other races.
As for winning expensive cars, try doing street races. When you get invited to midnight battles, you can win a few nice cars there. You can also win lots of cars from wheelspins.
I have done the Goliath race already, 4 times. (3x with 10 laps and using an CR boost car).
I will try out those midnight races, although, the first car I won there was an boring BMW. But who knows the next car will be better.
I used the Jaguar F-Type Horizon Edition. I can’t remember exactly, but I earned around 1,000,000 credits (10 laps) + many XP points (can’t remember how much) for many Wheel Spins. Again, I’m not sure but I went from around level 100 to 150.
If you have the patience, i managed to go from 300k to 30mill in an hour or so just constantly doing wheelspins. if you have some horizon cars you can sell duplicates for 5mill each, do that once, spin until you get another, repeat.