I'm kind of "want all cars in my garage" and "only buy the cars I want" as at some point I will have run personal TT's/hotlaps, maybe a custom one-make race, etc of pretty much every car in the game outside of extremely pedestrian FF's, sedans like the Atenza since I daily drive a Mazda 6 S, electrics, etc.
On top of that I buy at least three copies of every car that can have weight reductions, engine swaps, etc. I've got 653 cars in my garage (after selling 8-9 NSX Gr. B's and other duplicate cars I don't want) and have purchased 502 car for 469.9mil credits, and am at 80% collection. Pretty much every car I've purchased that I've been able to afford to tune has been used in some capacity.