62% game completion here. Great game.
1. Turn on auto-accelerate and auto-brake 100% except for rally.
2. Upgrade your car to make it faster than computer opponents and give you the advantage.
3. Running into computer cars can be useful, especially if you are on the inside of the turn.
4. You only need to get into the top 3 in each event to clear it. Watch the cars in front of you to get early hints on turns.
5. Watch out for tracks with "S" curves. You turn slightly one way and then the opposite. This is the only time hitting the racing line is critical.
6. When buying cars for specific races, try and buy the ones with highest horsepower and lowest weight from among the car choices available (hint: they are usually the most expensive).
Rally racing is the only part of the game I have not figured out yet. But I still manage to make the top 3, usually.