chunkwm and skhd combine a keyboard-driven interface and a tiling window manager to make the OSX experience as much like i3 as possible.
I use an app called SizeUp, and it works for me. I got it originally to mimic Windows' default keyboard behavior. It's free but gives you a message until you buy the license, which I did.
I then found out about Magnet, which as far as I know does the same thing as SizeUp. It's $1 on the App Store.
Chunkwm and skhd seem much more customizable though. Also it's free, which now I'm wishing I knew earlier about...
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