Keep looking, it is amazing what you can find. You should find a wealth of events of every type posted there. Check with the local Cooperative Extension Service. They are also very helpful if you need the quality of the soil checked or hay tested for nutrients. The people who work at all of these places are a wealth of information about the area and those who ride and put on events of all kinds.
Many areas have local freebie horse publications.
You should find boarding, breeders, rental, stables, tack, and trainers in just about that order. Be brave enough to call some of these people. Remember that those of us who share our lives with these animals love to talk about them and share our sports with others who own horses. Post flyers at all of the above places, as well as any local training barns or boarding stables that there will be a new group starting a month from a convenient date. Set the first meeting at a local Pizza place or other local meeting place.