Why do you need a second monitor?
Specs? (Of your PC and existing monitor)
Budget?
CPU: i5 4460
GPU: XFX r9 290 DP
I would mostly use it to just watch movies or netflix or youtube but my current monitor is an Acer - H226HQLbid 21.5" 1920x1080 60Hz Monitor. My budget is around 100-120 dollars.