My first quad that I built and my goal was to make a bando basher, easily portable, on-board recording, and hopefully sub-250g. I eventually gave up on the sub-250g requirement but very happy with the results! I'm still new to flying quads and been flying a lot more in 3D mode (this is why some of the props are on backwards). There are pictures of two versions, one with a Foxeer T-Rex camera and another with the Caddx Tarsier v2. I ended up going with the Caddx Tarsier v2 as I found it was easier to use. I also used some of the 3D prints from 3DKwadz - Gecko Parts and remixed the rear antenna. Awesome designs and suggest checking out their build.

Video of flight with Insta360 GO combination: Youtube: Gecko 4inch 3D Mode Flying

Motors
I tried three different motors on this build all from BetaFPV: 1805 2550kv, 1606 2550kv, and 1505 3600kv. The 1606 were my least favorite of the bunch, not enough power to do much of anything. The 1505 were actually pretty good, and for cruising did a fantastic job. These motors required a lot less power and preformed well. However, it was a bit a loose and the transition in 3D mode was sluggish. The 1805 is what I finally decided on and this decision ended up pushing the build over 250g. However, they are fantastic and feel great (as far as my relative new experience can tell).

FC and ESC Stack
Went with the Diatone Mamba F722 Mk2 Mini, and this was way overkill. Could have gotten away with the F4 and saved some money.

Camera
Quick word of caution! The Caddx Tarsier v2 does stick out slightly from the cage on the Gecko if you don't want the cage in view of the camera. Because of the dual camera it doesn't fit all that well inside the cage and angle adjustments are limited. Decided to stay with the Caddx Tarsier v2 over using the Foxeer and Insta360 GO combination. The Insta360 Go does give better picture with stabilization, but the Tarsier was just easier to use. I'm also not going for high def footage, just something simple to share with friends and keep for myself. The Tarsier v2 being half the price of the Insta360 GO makes it a much less expensive issue when I eventually crash and destroy it.

Props
I tried three props including the 4030 Nazgul, Gemfan 4023 3-blade, and Gemfan 4024 2-blade. All of which ran well. On the 1606 motors I preferred the 2 blade style and for the 1805 motors I preferred the 3-blade. My dream is to have some actually 4inch 3D props... if you know of any please let me know.

Antenna Mount
I'm very pleased with the underbody antenna mount I designed. I originally used zip ties but had them break twice on me. I also tried using the Immortal T antenna, but the antenna would get pulled up into the props when upside down (3D Mode). The mount I created seems to be providing decent reception and doesn't flex up into the props. The micro antenna by TBS would have probably been a better idea, but I had this on hand... so its what I used!

Update: If you use the vtx antenna mount I created, I would make sure the antenna doesn't stick out much at all. What I have pictured now is just a tad bit too far. The reason is during a crash there is just enough flex for the antenna to bend and hit a propeller. Make sure that it is short enough that the antenna would not hit a propeller during a crash. A little bit of tape or zip-tie helps as well to keep the antenna in place.

Other Notes
I used a 25V-470uf capacitor in the final build, and probably would suggest to others a 35V-470uf to be on the safe side. Please note that the rear antenna mount I designed won't fit the 35V-470uf capicator, as its too large.

Links
Gecko FPV Antenna Mounts
Gecko Insta360 GO v1 Camera Mount
Youtube: Gecko 4inch 3D Mode Flying
3DKwadx: Gecko Parts