I have never really played any extensive racing games. I played Gran Turismo 2 and 3, but that was ages ago and I never really played them seriously. My first opinion of the game was great graphics. With time I have been able to see the game more fully, and must say it is remarkably well done.
World Tour is where I started my journey. There are 10 seasons of career to complete. It is relatively simple to gather the achievements for this section. The races aren’t too long and you get a taste of all the classes of the Forza World.
The event list a compilation of the full experience. It has a lot of great races and offers a very hefty achievement for finishing first in every race. Warning there are a lot of races to finish first in. The event list is separated by class and you must complete all championships for all classes. This whole process will take hours and hours, but if you have trueachievements.com it will show up that the achievement is worth 635 true achievement points. This is one of the hardest achievements to get because of time. Good Luck.
Online racing has some great experience. That is if you can get past the fact that the largest part of the community will ram you off the road. This is why I am glad there was no need to spend any length of time with these people. I just played long enough to hate it and went back to career. There are no achievement for Online play, but there are several for selling some items.
The goal for achievement is level 50. Truth is if you pursue the World Tour and Event List you will get it very quickly. The cap is 150 so don’t plan on capping out unless you need to that is. If you have questions I have completed most of the game, and I have a majority of the achievements. Still working on the more time consuming ones, but getting there.