The best way to learn to set the car up is to practice. There's some decent guides out there to help teach you what effects you can create by altering certain settings, and from that it's just trial and error.
I hate all the WR sets, so I don't use them. I use all of my own sets and when I started playing I totally sucked. These days I'm using modified versions of the Race_S sets for most tracks. Sometimes I'll get the WR so I can compare gear ratios though, since I'm not so good with those.
And of course Bob's <whatever the hell the tool is called now> can help if you can figure it out (I couldn't back in the day)