This is by far the most difficult achievement in the game, but can be made much easier and doable using some techniques and tips that I used to complete it. You must start a Career session in the Highlands and play through all the worlds ending at the Peaks. As the description says, you can't bail at all through the whole session or you must retry from the beginning.
1) Don't pull of tricks or go off big jumps too fast as doing so will increase the likelihood of wrecking.
2) Focus on getting a couple good crew members at the start of you session, but don't be too concerned with scoring rep.
3) Take it safe and easy, it's not a race.
4) Practice the Canyon and Peaks boss jumps in freeride mode! Keep practicing until you feel confident you can complete the jumps at least over 50% of the time.
5) Crew members you want to unlock in order of importance are: Fewer Obstacles, Speed Wobbles, Landing Impact, and In-Air Correction. Not absolutely necessary but the are very helpful.
The most challenging parts to complete this are the Canyon and Peaks boss jumps. For the Highlands and Forest worlds, just simply ride around the boss jumps and through the finish line. You don't have to actually complete the jump to travel to the next world, but for the Canyon and Peaks boss levels, there is no way to navigate around the jumps.
For both the Canyon and Peaks boss jumps, you want to aim for a speed of 75 to 80 kmph by the time you hit the ramp. No slower or faster or you will under or overshoot the jump.
The more you play, the more you will know how to avoid close calls and wrecking by adjusting your bike certain ways as I did a few times. The video below is the run I achieved this that shows the general strategy I outlined. Also a few really close calls.