The above will take you through the whole process, step by step.
You need Device and Kernel repos as a minimum, which blobs and other things you need is largely device specific and depends on what/how the manufacturer has chosen to release stuff.
Generally speaking the rule is, if there is a CyanogenMod port for your device (up to cm12.1), then a sailfishos port should be achievable with the same sources.
Alien-Dalvik is unavailable on community ports unfortunately, although a community-based effort to provide a replacement is in the works but is currently at the experimental stage.
If you are serious about giving this a go, I highly recommend joining us on IRC in #sailfishos-porters on irc.freenode.net, there’s many people in there who can help you at any stage of the process.
EDIT: Sorry i’m being slow, this is the about the Fairphone…
To build Sailfish OS for Fairphone 2 we will need to wait for Sledges to release what he has done with the base android repos, as there’s a whole lot of patching in there needed for hybris to work