I've had little to no issues with my Spark , except for it responding to gestures.
1. I hold my hand up (Start/Stop PalmControl), it always tracks my palm and strafes left/right and moves up/down.  Drop my hand, it goes red and it exits.
2. I wave at it  2 - 2 1/2 feet away, and it rarely enters follow mode.  Maybe 1 time out of 10 attempts.
3. When I make a frame to initiate selfies, it rarely takes a pictures.  Maybe 1 out of 20 attempts.
4. Raising both arms in a Y to Beckon, works a bit better than most gestures.  1 out of 3 attempts.
5. Raising one arm at an angle to initiate video works around 1 out of 5 attempts.
6. Palm land always works!

I bring this up not to flame DJI, because I LOVE my Spark . But I simply want to know how to improve it recognizing my gestures.
When I show off my Spark , I want it to respond in a timely manner instead of me looking like a fool waving my hands and arms all over the place.  And onlookers thinking, "Yeah right, sure this thing is controllable with gestures".  I wanna feel like a JEDI and have this thing amazingly controlled.

I can tell you that my success has varied based upon ambient lighting and the colors of my clothes. You need to really stand out to the Spark for it to work.

I've had success with all gestures except video recording. Whenever I do the video gesture, it seems to recognize it as Beckon.

I also had one strange experience where a gesture somehow triggered a rotating quickshot, but I haven't been able to replicate that.

From my experience, it works best on sunny days. It will work on cloudy days, just not reliably - especially at max distance.
Edit - Forgot to add that you may want to make sure you keep the red lens free of smudges. I've had problems tracking and using gestures when there were some fingerprints I hadn't noticed at first.

There has to be high contrast between you and the your surroundings. So light, color of your clothes  and what is behind you matters. The worst gesture detection for me is on brightest days.

Unfortunately, the best advice I can give you is to downgrade to the previous firmware. In my case, gestures were all working fine until I upgraded. Since then, I'm very lucky if I can get the palm-follow to work. For the rest, forget it. Yes, it is that catastrophic. I really hope DJI can figure this out.

easiest fix i found for gesture control is not to use it....     i think i only used it like 5x to show off my spark to family and friends and impress them but that's about it, i enjoy flying it and exploring with it

@TheCyberKnight, I feel the same.  It was more responsive to gestures before the update.
@ImHereToCrash, I quite enjoy flying it and exploring with it as well.  Just would love to take advantage of that feature that make it the drone that it is marketed as.

I've been pretty lucky to have gesture control to work and much better response since the 4.1.5 update.  When working with your Spark, make sure you watch for the green lights.  If they are flashing, it means it doesn't recognize your gesture.  make sure you get a solid green light before moving/auctioning the gesture.  Don't move to fast as the sensors need time to process and react accordingly.  Be patient; its not perfect but works will with patience and slow steady moves.  good luck

lucsvette Posted at 2017-8-8 11:14
I've been pretty lucky to have gesture control to work and much better response since the 4.1.5 update.  When working with your Spark, make sure you watch for the green lights.  If they are flashing, it means it doesn't recognize your gesture.  make sure you get a solid green light before moving/auctioning the gesture.  Don't move to fast as the sensors need time to process and react accordingly.  Be patient; its not perfect but works will with patience and slow steady moves.  good luck

Again, like I mentioned above, gestures were working perfectly before the update and were impressing people.

Now, I have a hard-time just having the basic palm-follow to work for me. Nothing changed, just the firmware.

I'm starting to think there may be hardware variations for Spark and that could explain why some have few issues and other have them completely screwed after the update.

We all hope DJI can fix this. Quickly.

High contrast clothes etc are right when we talk Tracking , BUT the question was how to improve gesture and there are less to non contrast issues as this is done buy those infrared sensors that work with depth of field.  I can say i tested firmware .500 today on a soccer field and it was ~ different than .400 .
From One hand it DID recognize my Daughter  on .500 compared to .400 but Spark was more "itchy " and when higher than me in gesture mode tried to land as always on my palm the camera goes straight down and DJI mistress did informed me that "hand control active" ?!?! WHAT ? My hand was below the spark for palm land....

I'm going to post again as I've just had a ridiculous time trying to get gesture to work since the upgrade. I thought it was a s sunlight issue, since i got it to work once on a sunny day, but it just doesn't work at all when it comes to getting the Spark to move right. Every time I try it starts the video recording, or does nothing at all. I'm going to downgrade my firmware and give it another go. I'll be sure to post my results.

Okay, I can't edit my post, but i have downgraded and upgraded to check my results and they are as follows:

Neither work with a black shirt and an olive skin complexion. Putting on a white shirt? Big difference, the Spark responded to everything right on the first try. My conclusion: DJI needs to either update their instructions, or their firmware to recognize and respond to individuals with darker complexions. I'm caucasian, but I live on an island and have a tan, so yeah... Black shirt, no dice. White shirt, it works almost like the video - I still had a problem from max distance taking selfies, but to be fair, it's also 6:30pm here and the sun is starting to set.

First, please make sure that you are using the latest firmware with the drone. Besides, avoid wearing black clothes when using Gesture Mode. Please kindly choose a wide place with no or slight wind. Strong sunlight, strong wind or indoor area with no texture might affect the use of the Gesture Mode. Selfie can be activated when the distance is within 7 meters, please check the distance between you and the drone.

mmatos Posted at 2017-8-8 04:13
I can tell you that my success has varied based upon ambient lighting and the colors of my clothes. You need to really stand out to the Spark for it to work.

I've had success with all gestures except video recording. Whenever I do the video gesture, it seems to recognize it as Beckon.

Gesture video recording can be initiated when the distance is within 2 meters. Please make sure about the distance between you and the drone, and hold one arm up and wait for recognition from the drone.

dezign999 Posted at 2017-8-8 14:42
Okay, I can't edit my post, but i have downgraded and upgraded to check my results and they are as follows:

Neither work with a black shirt and an olive skin complexion. Putting on a white shirt? Big difference, the Spark responded to everything right on the first try. My conclusion: DJI needs to either update their instructions, or their firmware to recognize and respond to individuals with darker complexions. I'm caucasian, but I live on an island and have a tan, so yeah... Black shirt, no dice. White shirt, it works almost like the video - I still had a problem from max distance taking selfies, but to be fair, it's also 6:30pm here and the sun is starting to set.

Please refer to my reply on 13#. Our engineers have been working on the increase of the gesture recognition, and it had an improvement with the latest firmware as you can see it in the release note. Of course, we will continue working on it. If you can not use gesture mode well, we appreciate that you can make a feedback to us. Thank you.