I'm involved in a local parent group. It was started long before my joining but as people's children get older they generally drop off so we're always looking for new parents to join so some of what we do might spark some ideas.

- we offer children's programming offered at "bright and gifted" children. We don't require proof and it works out fine enough. You could start small with something like meeting at a public library for chess or something that wouldn't require a lot of set up organization. Eventually, over time, ours evolved to have paid instructors and span multiple weeks. While the kids are in classes there is a parent room for parents to chat and sometimes speakers are brought in. This is probably our biggest draw. Local psychologists give out handouts for our organization and activities when they find gifted kids.

- we run gifted 101 and 201 sessions for parents with details about testing, advocacy and gifted programs in the area. This started out as a single night but we ended up with too much material so we eventually split it into two - one catering for those that are thinking about testing and are starting out and the other for those that have been through testing and are wondering what to do (or are looking for more tips because they haven't had any luck). We offer each session twice a year and get decent turnouts (we're in a decent size city). Advocating here is a challenge so parents are pretty desperate for help.

- a local gifted parent facebook group - highlights events in the city that might be of interest as well as articles and resources that might be of interest

- pub nights - we advertise through our mailing list and facebook and pick a local pub. Most parents are happy to finally be able to speak to someone about their challenges because let's face it there is a lot to this that you can't complain about at the playground.

Depending on your school district, you might be able to get the word out through them. My suggestion is to offer something (start small - something like a chess meet up or pub night that is low organization/risk) and hopefully get a few people that you can grow things from there. Good luck!