Off-Brand Lenses

So I'm in the market for a nifty fifty lens and while looking through Amazon, I found a Nikon lens for around $200. But after a bit of searching I found an off-brand lens that claims to be compatible with Nikon for almost $100 less. Ngl I'm tempted to buy it but wanted to ask what you guys think about off-brand lenses. Is quality much of a difference? Does it even matter? Is it alright for beginners like myself to buy off-brand lenses? Or should I save up to buy the lenses from a reputable brand like Nikon?