I have some issues with GTVault:
1) As you've discovered, there's a lot of crap. You will have to wade through a mountain of dung to find the occasional ruby. However, as you knock around there more and more, you'll find that there are certain tuners whose work you can generally trust. You'll also start to identify the n00bz that think because you get up there and start changing crap randomly, you are t3h gr8 t00narz and they'll copypasta the exact same setting to ALL cars in the game. Usually, if I open a post for a certain car and notice in the upper-most field that the car is equipped with R5s or St.4 turbo, I move along and look elsewhere. It's probably junk.
2) "Different strokes for different folks." Reubens Barrachelo and Michael Schumacher used to be teammates driving for Ferrari in 2005 and thereabouts. They drove the same car, but I promise you they had different suspension settings because they had wildly different driving styles: Reubens was very methodical and cautious, whereas Schumacher was a man possessed. You will no doubt have to make adjustments to any settings to get the best results for YOUR driving style.
Finally, 3) there is no "magic bullet" as far as suspension tuing goes. You can't expect to drive a 12 minute lap around the ring, throw on a new tune and see it drop to sub-5s. The purpose of a suspension tune is to make the car more stable, predictable and driveable on any given road surface. Approach angles, lines, etc. all change from course to course, and car to car, and driver to driver, so your priority should be finding the tune that has that "natural feel" for you. If you find the car to be substantially less quirky and/or twitchy, then mission is accomplished.
Tuning is not dissimilar to long-range shooting and reloading: someone else can give you general information to use as a starting point, but there is substantial difference between how we shoot, and our rifles, and our exact components, so you have to season to flavor to get those tight, itty-bitty groups at long range. It's just a matter of "dialing it in," as we like to say on the shooting range.