So, from my understanding, when I am upgrading an antenna, the higher the gain, the worse coverage it gets in some directions?

I have 2, 2.4GHz 8db gain omnidirectional antennas, I want to put one each on the range extender and the controller. Are these antennas bad? Should I get a lower gain? I'm not trying to do anything extreme with the phantom quite yet, I may in the future, but I have noticed the signal on my phone came and went on occasion. What do you recommend? Thanks for your help!

I suppose a good place to start might be http://fpvlr.com/

The have whiz-bang stuff I never even heard of before like a "Left Hand Circular Polarized 2.4 GHZ Parasitic Disk Helix antenna".  Man, if that's not a mouthful I don't know what is!