Wah, going to be really expensive to get auras for all the cars
you mentioned. Not easy to challenge people you don't know as they
might be very good. And if you just challenge noobs, it will take a
long time as well as many races, not to mention it means your aura
comes without skill. If you just challenge your friend, also not
much challenge since can 'agree' who win the next race. Also your
skill level will stagnate with your friend.