You make money by racing other players and delivering tofu. I would not recommend doing player races sinds the amount of money you get from it is bugged. If you win you get between 100 and 200 yen, and if you lose you get nothing. you are better off delivering tofu. Best places to deliver tofu would be haruna or irohazaka. These both give 140 yen and akagi only gives 70. The other might be longer, but you can't finish akagi twice in the time it takes to run haruna or irohazaka.

Simple, get a car you like and tune it cuz
All cars have same stats except their chassis is different, meaning different weight and hitboxes. So basically the inside is the same but the outside is different.

2 kinds of tuning:

Performance:
Power -> Top speed -> capped at 320
Brake -> stronger brakes
Torque -> Acceleration
Start leveling torque and brake before power.

Turn off rev limiter in engine setting. This causes problems with the automatic gearbox.

Handeling
Wheel camber: A developer has confirmed that this does change the handling of the car. I have tried a lot of different setups but i completely don't feel any change.

Suspension: To get used to the game put these on 0.1 on the front and 0.2 on the back.
You can really play around with these settings since there are only 3 options for front and back. These also differ from car to car because of weight .

Some fun settings i have found for my civic is a drift build
0.2 0.0 seems like a drift build
0.2 0.2 feels like sega rally but is really unstable and bouncy

Options:
Steering sensitivity -> max
Steering helper -> max
steering helper applies automatic counter steer when you drift. I highly recommend this for beginners

You might not know it, but if you press B on your controller or Shift on keyboard you can boost, its like NOS in need for speed.
On these mountain passes you need to be very careful how you use your boost.
You want to use your boost on long straights or to give you extra speed while coming out of a corner.

When starting a race, boosting is the norm, I discovered that boosting in 1st gear is not so great, it just makes you hang longer in gear. Your best of waiting till your cars is in 2nd before you start boosting

In IDO you have 2 ways of breaking: Handbrake and normal pedal brake.

Only your normal break will actually reduce your speed enough to take a corner. The handbrake is a mere suggestion of deceleration and is used to get your car sideways