@icearmor The only way to make money is racing any time every day, it depends which races are you choosing, I'm farming every day for gasket, battery, Ferrari BP and McLaren BP, the last races for gasket in Chapter 11 they offer 6.5k and 10k as a gift, and the Chapter 14 (Boss) sometimes offer 12.5k and 15k, battery races offer from 6.5k to 20k, so every day I got around 250k cash between races prizes and gift from crates, but I'm racing almost every time my fuel and tournament tickets are refill, if I'm lucky somedays raise 350-400k but need to use all fuel and tourney tickets available.
Not magic at all, only race on every single opportunity you have, wait for all access pass and farm cash, my recommendation for you is you should get the Viper, those 25k difference between Porshe and Viper are a lot, depends how many restarts you have but if you have 1 are 50k, 2 are 100k, 3 are 150k, 4 are 200k, so 3 times a week the difference is huge.
I'm upgrading parts from purple to gold and almost never need to farm anything else but gasket, relay and battery, the others materials come from TT and free crates (every week I spent between 500-800k cash buying normal crates, easier than farm for everything, because almost never refill my fuel with gold.
Happy racing!!