For my first build, I wanted to get my head in the clouds...
This means FPV camera on a 3 axis gimbal, head tracking and long range.
Designing the gimbal mount was an adventure as I used Fusion360 for the first time, it is a bit buggy and took me 10x the time it would in Maya but look at those wonderful bevels!
Logic behind the choice:

• R9 for the long range, it's cheaper than xfire. Also they are not as dependable which isn't good for long range but they're "working on it"
• Separate ESC so if one burns it only costs 8$, the flycolor raptor have been around for long, are dependable and very low noise, also long range is better in oneshot or multishot.
• the Matek F405 is old enough that it's been well debugged, it is also very well supported by iNav and the layout is simple, also the drill through hole for most pins make for sturdier solder joints. Edit: I stopped soldering through hole and all is surface soldered because it's easier to work on when the FC is fixed to the ESCs
• the HL7 is almost never used, the reason is it vibrates a lot and the FC accelerometer struggles with those extra Hz.
• I went with the 1250KV recommended by Pawel, they are very smooth and powerful
• Beitian BN880 has mag and a fast GPS that inav uses for navigation.

Getting this monster in the air was difficult, some people trying to help me with the log pointed at the amount of resonance from the frame. Once I made the frame stiffer it was flyable, as a first quad this was a bad idea, the gimbal didn't take well the hits. I ended up removing the gimbal and going locked cameras. Flying at ground level was fun, I was about to coat the FC and ESC with Conformal Silicone but got caught by the thrill of the flight, drizzle turned into rain, the quad short circuited. Lesson learned.