I got all-Silver on all the Licence tests up to IB.
Then I used the Honda Dualnote (all-Silver on A) on Capri Rally Easy (only wortha few points, but I suck at rallying), got the RSC Rally Raid '02 and sold it for 250,000 credits.
Then I took the Mazda RX-8 Concept (all-Silver on IB) and won the RX-8 Championship to get the RX-8 Race Car.
In all, I got 300,000 credits and one mean beast of a racer (if slightly ugly, that orange/green paint job doesn't do it any favours). Now it's simply a case of buying the right cars for the right races to get A) a sufficiaent challenge in each event and B) 10,000,000 credits by Day 694.