3 monitors are usually no problem to work with just the motherboard and the integrated graphics chip of the CPU.
So you won´t need a dedicated graphics card for 3 monitors.
For four monitors, you can get something like a gt 730 or
for better resolution and video output quality with integrated H.265 encoder: the gt 1030
with this constellation you would plug in two monitors in igpu and two into the dedicated GPU or 3 and 1 or 1 and 3