100% agree with @peterB ...
At the begining of your trading career, one screen is more than enough as you still need to start the learning curve with hotkeys and the platform + the chart reading + pattern recognition + L2 reading + etc
Whenever you start doing some more practice, you can jump into a setup of 2 monitors or just 1 bigger one. It all depends on many things and IMHO is too personal to decide based in anyone else experience.
I totally disagree with the idea of having 4 screen at the same time. Too much info. Only "professionals" with +5 or +10 years of experience will manage that amount of information properly. Most of the cases, they will do more wrong than good.