The usual extra info on this series, for the BMW M2 Competition, plus 2012 Audi TT and Nissan 370Z NISMO...

There are 51 events (48 Trophy + 3 TT) with each car having a specific two-event showcase + TT.   The rewards 25-50-75-100% are split 6-9-13-20GC, with only the BMW able to be upgraded enough to complete the series.

You can't reach 75% with the Audi alone, fully upgraded ...

...but I'm pretty sure you could with the Nissan fully upgraded - sadly I forgot to emulate that option  .  With both fully upgraded you can do all except the BMW Showcase/TT and the final three Cup races ...

 

The costs of upgrading the BMW enough, and indeed those of winning it in the LTS, are as below, as usual courtesy of Paulo over on Facebook RR3 Trackside:

And now I guess I'd better get started on that!!