As far as I know there aren't any setup depositories around anymore, 10/12 years ago there was a huge one, but he shut his site down after too many complaints. It is far easier to do your own, in the download section I put up the guide I've used for years, the only thing missing is gearing and that's usually one or two clicks away if you use the expert or fast setups that come with tracks.
To get to where you should be able to keep up with most drivers online use the fast or expert setups that come with the tracks you need, it's going to take some time to get there, there is no quick fix. Set the A.I. at 100% and you should aim to be running a top 10 to 15 time with consistency.