I always use dual if not quad nics and I do that for a few reasons. Dual nic's are great for integrators providing a turn key solution with a network switch, and not using a customers network, it allows you to physically seperate the networks at the nic. Cameras on one nic, viewers on another. Option 2, NIC Teaming, that is easily done through windows server 2012, or if your using broadcoms they have a software download that will do it, you just team them up and you will get thoretically 2Gbps. Also it will offer redundancy, so if you lose a nic, or a switch you dont lose your connection. also if you want to get really creative you could set up 4 nics, and designate 2 of them for download, and 2 for upload, but thats just overkill for 99% of things.
There are a few methods of NIC teaming, Switch dependant and Switch Independant. One requires configurations on the switch, one requires the configurations on the NIC.
Below is a basic explanation from Microsoft.
NIC Teaming Overview | Microsoft Docs
Regardless, always use 2, because if you don't need it today you will tomorrow. Nics are cheap, and they will save you headach and give you more options.