Note: You MUST choose the hardest difficulty when starting the game. You cannot change it later. You can still retry every stage as often as needed, so it shouldn't be too bad most of the time.
There are four types of stages. Race, Drag Race, Freestyle, and Destruction.
For each stage of the event, you will earn a certain amount of points.
... - Not Important to winning.
Most events will have 3 stages. These are the best ones. If you place first in two of them, and last in one, that's 31 points. Opponents will place randomly every time you go through, so on the event you lose, make sure the top 2 or 3 point scorers place lower down. You can restart the event as often as you'd like. Using this, if you are good at two types of stages, you can win pretty consistently with minimal effort. For example, I would win the race, flip over instantly in freestyle, and then win the drag race.
In events that have 2 stages, you will have to place first or in the top three on both, given other racers do not place the same.
In events with 4 or 5 stages, you can win all but one, and come in last again on the one you like the least.
There are 30 events in the game, 10 in each league. As long as you buy upgrades when unlocked in the shop, most events won't give you trouble. As for the others, you'll be restarting the stages quite a bit. Find a route that works for you, and run it. Eventually, the physics in the game will match up with good inputs and you'll get it. Good luck!