Amplimator

Evenin everyone, this may seem like a daft question to some but im considering a enduro/crosser for a winter hack and a bit of green-lane action but im wondering what does it take to make a non road legal one legal? i know i could just buy a legal one but generally non-legal are cheaper, but is it a false economy making it legal?(ie end up costing more) do non legal come with a V5? does it just need tax, a V5, a speedo and an MOT? (for daytime MOT) i know indicators only have to be present if bike was built/designed with them but what about the rest? etc etc etc

this will be my first 'dirt' machine and basically i have no clue, theres a few local to me but not road legal so any input greatly appreciated

thx