Honestly... If your looking for randoms, Just set up a room with clean in the title at a level people generally like to run (550PP) on a popular track (Nurburgring, Grand Valley) and scout people without there knowledge. If you see someone with what you are looking for (cleanliness, speed and friendliness) just ask them if they're interested. The whole purpose is a lot easier if you and your friend use mics and have some casual banter going on. It sounds weird, but these people are basically scouting you too, so if they know your a relaxed and friendly casual pair of guys who talk maturely about topics that are interesting, and race up to a high standard, chances are they'll jump on your league proposal. A side note though- You have to remember that some people see joining up to a website etc, etc to be a big hassle. Displaying what they want to see is essential if you desire success. In other words, don't abuse someone if they make a mistake or make jokes about peoples PSN name or country of origin because people are easily offended and will tell their friends about any bad experiences they've had with certain people online.
If however you're recruiting people from here.... You should move the thread to the online racing section, put some serious thought into what you guys are about and make a flashy and clean OP. I honestly wouldn't bother giving people from here try-outs, if they're still on this site nearly two years after the game was released, I'm pretty sure they'll know how to race well.
In short: Don't be a tool, use a mic, set up racing people want to participate in and put a lot more thought into the endeavour before you pursue it to thoroughly.
EDIT: One unrelated thing I have to say- Type on this website like your writing a letter to your grandmother. Would you say lol more than once in a sentence to your granny? Probably not. Would you, however, use capitals and punctuation? You know where I'm going with this...
. As for the type of people, in my opinion. A clean racer, Aids or not, driver preference or your preference. Pick a track that it kind of technical yet at the same time simple enough such as Madrid or Spa(if u have Spa). The type of car depends on the type of racing style I guess. Street league racing use low PP cars. Or Lemans Cars. Not sure on that one 
