@Pedinhuh If you're looking for completeness, get the invite cars when you have an invite; you never know when/if you'll get another one. The Hagerty's cars, unless PD jumbles the rotation, come around ever 2 1/2 months.
As for what I did, I started on the GTP account, and immediately claimed my X2019 25th Anniversary, 250,000 Cr. from bronzing the old online time trial, engine ticket from the Nissan Skyline GT-R extra menu (as I had the extremely-time-gated 1970s Skylines, with the 1970 currently available in Hagerty's) and parts ticket from the Renault extra menu (as I had the extremely-time-gated R8 Gordini). As I was hoping for the Escudo engine so I can see how much more the Escudo is going to cost, I opened up the tickets, and got the ultra-high rpm turbo for the RE Amemiya (which I didn't have before) and another Rampage engine.
I jumped to the Plus account to get the extra menu tickets there, and also the X2019 25th Anniverary and the price for the Pikes Peak engine. The parts Wheel of Despair gave...wait for it...wait for it...the ultra-high turbo for the RE Amemiya (which I already had on this account) and the engine ticket gave the 2008 GT-R GT500 engine (at least I didn't already have that).
Going back to the GTP account, I was surprised to see that only the Super Formula cars had their PP calculations change, and that, for the Hagerty's cars that I have that have new engines available and the 3 that are the bases for engine swaps (thanks
@Scholid for the Escudo engine recommended price), the Hagerty's price increases aren't, in the cumulative sense, overly excessive, though there are a few 20%+ increases in there. Before buying the Sierra Cosworth (surprisingly in the UCD) and Silvia K's Aero, I unloaded a few cars on Andi.
I then tried my luck on the special races. I used the BRZ on RS tires on a dry Spa (the rain was still headed in by the time I finished) to crush the field (on normal) in 23:56. The RS tires lasted just as long as the fuel did - 6 laps on FM 1. The race at Big Willow was closer, but 7:55 later, I was another 1,800,000 Cr. richer.
Some more cash was earned by eventually golding Road Atlanta. The first sector was a real struggle, but that hill near the end is also a real killer. I called it a morning by collecting a stage 5 weight reduction for the 2017 Nissan GT-R NISMO and buying the now-overpriced 1995 McLaren F1 GTR (which I was short by over 1,000,000 Cr. for yesterday).
I'll be back to do the Plus account.