I think it might depend what you're into, I don't know much, I've flown my Mavic mini a few times, and have been watching the Ukraine war at a distance.

But if you're into photography and videography you might get more enjoyment out of something like a 249g Mavic that has a solid camera and is an overall very solid drone.

If you're more into sports and piloting, you might have more sustained interest in an FPV drone where you use goggles to see through the stone's eyes as it flies. In that case I've heard good things about the DarwinFPV drones as they're a pretty dirt cheap entry point and you're likely to crash them.

In terms of usefulness for civil defense, I'm guessing that the most useful skillsets are probably FPV flying and drone building and repair, but I'm not sure. In Ukraine it seems like they use some off the shelf quadcopters like mavic minis for basic reconnaissance and observation, and then use FPV drones for carrying munitions and striking targets, and those are a mix of quadcopter style and more plane style.

Another option for civil defense preparedness is to do first aid training.