Complete the second story mission to get the ability to participate in street races. You will be matched with random players. You will be rewarded with money if you win, which can be used to upgrade your car.
Shifting
Watch the tachometer's needle or the number gauge to know when to shift. When you are nearing the correct area to shift, a yellow light will blink under the numbers. Once it reaches the best area, it will turn green. Earlier shifts are usually more difficult because of how often your speed changes while in lower gears.
Starts
The starting boost is slightly difficult to execute. Proper timing is required, as any tap of the gas will rev your speed. When "3" appears in the pre-race countdown, time your revs with the appearance of the numbers. If timed correctly, your last rev should be timed so that your tachometer's needle is in the middle, which results in a perfect start.
Upgrades
Normal upgrades and the occasional blueprints are awarded for winning races. Blueprints usually give you better boosts than normal upgrades, however they usually also affect something else negatively. Consider all changes that come with an upgrade before applying it. You can also sell blueprints for gold coins, the game's premium currency.