What is the best all around car and tuning setup for a majority of the career races? I am a beginner when it comes to tuning setups, but have been playing Forza since the first game.
If you are afraid of tuning, then don't. The game will choose recommended cars for you and pre-tune them for the specific career section you are entering when you purchase it.
Every car in its league is competitive enough that there is no clear cut best, although some cars will have a slight advantage. These are usually the ones marked "recommended"