...that You use xbox gamepad for driving so the first step is to use the wheel
A
wheel will no doubt help in endurance racing, but regarding sprints, you can get away with a
gamepad/
flight yoke very well (even
keyboard)...
In my opinion the biggest "advantage" a
wheel (and
pedals) has to offer is that it is more "real"... and to me, that alone, is more then sufficient to make it a “must”
On topic
Regarding cars... you will see that with some, it is easier to achieve certain lap times (although theoretically all are capable of doing very quick times around the
Nordschliefe).
The quickest times around there (not in race and many set in "
time attack" mode) are at very low
20's. Going under
30 puts you in an already restricted club. Having a race pace around mid
35's will most likely give you a decent chance of doing well even in presence of stiff competition.
Your choice of car, the
DB9, is a common one in the public servers... so look for an
online setup for it. There are quite a few that give you low
30's lap right away.
By trying different setups and comparing how the cars handles with them in relation to default setup can give you good pointers as you see the options/settings the setup creators took.
Just to finish, obviously you need to know the track with your eyes closed before attempting to go “faster” and testing setups… well, maybe you don’t “need”, but
it is advisable