By far my favorite filmmaker gathering has been the Film + Music Conference put on by the Musicbed and Filmsupply family in Ft. Worth, Texas. Their 2017 event was the first one and I'll be attending 2018 as well. It was crazy inspiring, really well put together, and I got a chance to connect with a ton of people I've met online or in person over the years as well as make new connections. Totally worth the price.
Masters in Motion (Austin, Texas) was a great place to meet with filmmakers, but expensive (for me); I've been a couple times.
I've been out to NAB a couple times and was honestly disappointed. Great to see all the gear in one place, but I had a harder time trying to connect with filmmakers vs. "people looking for gear." Plus you have to deal with being in Las Vegas...
I've not been to Cinegear or Cameraimage, but they're both on my short list.