Welcome to FC!
$50 isn't really a good budget for a vaporizer. Most vapes in that price range will actually combust your herb and will not vaporize. If you really need to stick to a $50 budget, I suggest considering a used vape.
That said, here are two vapes in the $50 price range to consider, both require the use of a butane torch to work (eliminating the complicated electronics means its a cheaper more reliable vaporizer, but means you can accidentally combust if you overheat the herb). - Vaporgenie Classic & the Triihouse Peace.
However, if you can bump up your budget to $75, then I would HIGHLY suggest you buy the Flowermate V5.0s. It's the nicest portable electronic vape I've used in the sub-$100 price range.