Yeah, that's the economic (read cheap ass) way to progress.
Thing is, at 4.0+SR in any one license level, you can race up to the license above. So you can race Rookie until you're D and then keep racing Rookie cars until you're D4.0 then buy the C car. Race C until B and then keep at it until B4.0+ and you can (again) skip a whole license level. Getting to NOT wear the brown (D) and green (B) strips.
Pretty bummed to hear mr. Millions isn't a 100% Content Buyer.
On the oval side you can get to B without buying anything.
Race the StreetStock rookie, till you get to D 4.0, then race in the StreetStock C-class series.....
I'm pretty sure I saw Alonso race in F3000, he won at Spa, that was the B-class series back then