I think part of the lack of success is the too short of a timeframe from posting the event to the date it'll be held. This is especially true for cars/tracks/combos people seldom drive and even more true with (mod-) tracks that have been uploaded for a very short period of time.
For reference: we had Nürburgring and Mugello for months - Watkins Glen and Mosport Park became available on June 1st and June 2nd respectively.
Possible solutions:
- Inrease the time between posting the event thread and the event date itself, reference:
EU - GT3 @ Mosport Park was posted on Wednesday, date for the event is Friday
EU - GT3 @ Watkins Glen was posted on Wednesday, date for the event was Thursday
- Announce a couple of weeks prior to the events with mod- tracks, which ones we can race on, you may make a bulk list - people have plenty of time to practice/prepare this way
- Street cars: make sure the performance is as close as possible between car choices, reference Akis post
http://www.racedepartment.com/forum/threads/gt-almost-3-mugello-tue-10-june-2014.88557/#post-1741157
- If a low number of people sign up for a particular event, maybe the event date just didn't fit the schedule of people who were interested in it - ask them on what day they would like to race; offer a choice between dates
- If it's a new track, set up the 24/7 server for it, suggest practice sessions
"We want to diversify our race combos. We would like to encourage you to try the following cars / tracks .... and give us feedback."