Wreckfest

In the first career category "Regional Juniors" you only need to complete 5 or 6 events to get the 1200 points you need to advance to the next level in Career. For the sake of getting all of the achievements, you don't need to complete EVERY event inside Juniors or Amateur or any other level of Career. You also don't need to complete the bonuses or challenges within each race. For all the Career achievements, just achieve enough points to advance to the next level of Career and move on! Don't waste time finishing every race, there's no achievement for that.

There is an achievement for acquiring 20 cars and some events reward a new car. Look at the rewards and if it gives you a car you should complete it to unlock some cars faster without spending all of your Credits on buying each one individually.