A diversity controller connects to your receiver, and gives you the ability to use two, when you could only use one. The diversity chooses the better signal, then uses that to "receive" whatever. Cheap ones cost around $50, but RcModelReviews builds one for $1.29. Not saying it doesn't have drawbacks, but it sure is cheap, so who cares? I'll be building one with my own tweaks and upgrades, i'll be putting it on a pcb (he dead bugs it), and putting it in a case. it should look pretty nice when i'm done. IF I GET 30 LIKES DURING SEED FUNDING I WILL BE GIVING ONE AWAY!
I have to take this log to apologize. I'm super new to all this, which i hope surprises nobody, and i did some further research. A diversity controller isn't something you plug two antennas into then into a receiver. It takes the video from two RECEIVERS and it chooses the signal for that. Due to this, I won't be using it for my goggles (https://hackaday.io/project/83624-diy-box-goggles-for-cheap-fpv) , at least for right now. If I try hard enough, i can find some $5 receivers, but they're only for lcd screens, not android. Maybe the only difference is the connectors, but i'd rather stay simple for now.
On another note, before I stopped this project, i did some work, and there is nothing more satisfying then adding a few toggle switches to an altoids tin.