It's worth pointing out that they upped the amount of credits you get per race with the last update. Also, they gave everybody 1,000,000 credits for the outage right after the game came out. They also seemed to give out three really high level cars with this last update (though it says that they are preorder bonuses - I definitely didn't preorder though).
I've played for around 8 hours so far and have coasted on creds that were free. You can approach it like a pay to win thing, but I don't really see it that way. They give you the cars you need in order to win races and progress. If you focus on fine tuning cars (not just buying upgrades that raise PP), you can get through any of the races using the cars you get for free in the game. They also incentivize you by giving you +50% prize creds for not playing the game like it's Mario Kart and running into everything (clean race bonus).
My session was ruined by the server maintenance the other night. There is no way around the fact that the game being unplayable while you're offline sucks. I don't think anybody will disagree with that.