Once you start winning your races, do not continue to use your merits to upgrade your class E car. Save them for when you reach class D so you can upgrade your class D car a fair bit- it will help a lot. Also, make sure to test a few cars out before deciding which one to upgrade :)
I upgraded my class E car to the point i was half a lap ahead of everyone else every race, I thought I was the bomb- but then was suddenly boosted into class D with only enough merits for 1 upgrade, and even with a top end car it's not proving to be enough to place first second or third. So it's a long slog.
it forces you to move up. gaining driver skill is unavoidable, seem to be getting it no matter where placing in a race. Seems the only benefit is you get to use more advanced cars. I've been wondering to myself what is it all even for. I guess when you finally get A class a car n do it up all fancy ur in with more of a chance to win the big money custom races. I don't know a lot about the game so not sure where cars are used aside from racing or crime.
You should spend either zero points in E class, or 1 point (for the strip-out). Other than that, save your points until you move up a level. If you have points to spend, it means you placed in top 3 in at least one race - and you did it without any upgrades. If you just keep racing, you'll continue to place top 3 (sometimes, not every race) without any upgrades at all.
You don't move up in driver class based on driver skill. You move up based on how many racing points you've earned in official races.
So you could avoid moving up by avoiding official races. Though I wouldn't recommend it.
As far as I know, which cars you have and your driver skill and such have zero correlation with crime success.
The only real benefits from racing are the merit points. There is one merit point for reaching A class, and one for winning 250 races with the same car. Other than that, there isn't much point in racing unless you enjoy it. (If you don't travel a lot, there isn't much downside to racing a lot, either.)
Pretty sure Ched got this idea and setup from another game he used to play, but there you can do other stuff with the points and sell them, so it's a little more rewarding to your account.