The usual extra info...
There are 42 events (36 Trophy + 6 TT) and the rewards 25-50-75-100% are split 9-15-20-31GC. You only need one car to complete the series, and the LTS-winning PR reaches well past 75%:
Needless to say, to get that little bit further to 100% will cost a lot more gold - 465GC I understand