At my current playing rate (only about 15 levels/yr) it takes me several months to accumulate enough G to buy a new car.  In going thru the many series I haven't been able to run, I discovered that the Porsche 911 "Clubsport", which is used in BOTH the "Masters of the Track" and "Peak Porsche Performance" series, was on sale for just over 500G which was exactly what I had.  Most of the recently added Legend-level series use cars that cost at least 1000G so I was quite pleased to come across the Porsche. It's been quite a while since I had one, much less two, new Legend-level series to run. 
P.S. In the "PPP" series you can't past tier 3 on just the 7 R$ upgrades.