There are a lot of articles and quizzes online designed to tell you if you're a Libertarian and just don't know it. I'm not sure Gary Johnson, the Libertarian candidate for president, could pass any of them. He certainly doesn't strike me as anyone who should be president even though I agree with some of his positions. So do Clinton and Trump, by the way.
Here's a piece on where Johnson stands on the issues. Frankly, I see very little to recommend this man for the job. If you're a real Libertarian — as opposed to whatever he is — you might give him your vote to hope that the party will remain viable and might someday have a candidate with a chance. If you just want to cast a protest vote against the two main candidates…well, that doesn't sound like a good reason to me.