Have you spent any money yet? I have managed to avoid it by playing old levels against friends to earn bonus points, but it's getting to the stage now where it's getting tough to earn enough money to upgrade or buy new cars!
Oh and you're too good at that bloody game!
Nope not spent any real money and I'm not going to! R$ can be farmed at R$40k per race in the accolade open (last race, Suzuka I think) which takes about 8.5 minutes using the "set the clock a day forward to receive an extra 100% daily bonus" thing, still freaking slow considering the Agera is R$2.3mil! It's gold coins you'll struggle with and have to pay a lot of real money for if you want to complete it, my advice is not to spend it on anything you don't have to to progress and save it for the Zonda-R and Agera-R, you'll still be short though.