Now that there's another fresh new option for a fun race to grind, I was able to push my credit balance from 2 million to 9.5mil within a few hours today and I went and bought the BMW M6 GT3 and the Audi R18 TDI for the sake of those two Scapes trophies.
I would say I'm barely, very minimally stingy. My strategy has been to buy all the UCD cars I'm missing as they come, except for the ones that can also be found in Brand Central. I rather get those from Brand Central, because the paltry discount for the amount of mileage they come with in the UCD usually isn't worth saving over. Eventually that car might need an overhaul or two and the overall cost to maintenance ratio would be higher on the used model when assessing how much I'd actually ever drive the particular cars, making the discount moot.
I buy all the Legendary cars I can afford at a time, starting from the cheapest and going up. I have missed a fair few already, but that's okay because they'll show up again at some point or another. I skip over ones that I don't see the point of buying now that I know I won't have much of a reason to drive at the moment, and will defer them to the next rotation. For example, the Barker '29 (the 13million Benz). I don't think I'll have any use of that car anytime soon, so that's further down the line if anything. I put any car I know I won't get this time around on the wishlist.
Finally, I had a goal of obtaining all the Invitation-Only cars from Brand Central before their eventual expiration in mid-May. Last night I achieved this, which felt good because I know how crappy the odds are of getting invitations in the roulette, let alone all of the invitations at some point or another. Now that I've satisfied that stupidly low loot-box-type-acquisition-of-cars-chance-element-due-to-invitation-only-mechanic, I can rest easy knowing all the others will be just a matter of time/rotation and having the credits at the right time. Unless, they do something dumb like add more cars to the Invitation-Only club.
I do eventually want to own all the cars in the game, but I'm fine if it takes me years, because that's how long this game will probably last me.