A quick point
I've just settled down with Mint 17.3 MATE which is LTS to 2019, after 3 years on Mint 13 which was LTS to 2017. To my surprise, based on the official Linux Mint site, it seems that Mint 18 will be released in May/June of 2016 and will be LTS to 2021. They are 'looking into' ways of making an upgrade path from Mint 17.3 to Mint 18 so that a fresh install isn't needed.
For some people, it might be better to wait until May/June this year and start with Mint 18. However, it's free and easy to 'play' with 17.3 and make a total mess of things while having a 'learning experience' to get you used to Linux if you've never tried it before.
Go on, do it, break it in many different ways, swear at it and learn how to restore it; it's not difficult.