Hello and welcome to my guide on choosing a proper monitor for under $100. Now, don’t expect the sky when you pay these kind of monies, however, you can definitely find some quite decent, full HD monitors.
Some monitors have the free sync option. Personally, I haven’t tested whether this function actually works like the G-sync counterpart from nvidia if not mistaken.
Free sync is available with AMD’s graphic card, so if you have this an nvidia GPU, this option is redunant, at least that’s what I understood from my reading. But yeah, perhaps I might be wrong, so ignore me, and make your own diligence.