I think there's a few things to look at.
Firstly you need to decide between a VM software that runs on a general purpose host (VMware workstation/player, the 'desktop' Hyper-V varient or Virtualbox for example) or on a special purpose host (Hyper-V server or ESXi)
Firstly, AMD and Intel have broadly compatible virtualisation extentions.
VT-X (Intel) and AMD-V (AMD) are the 'basic' virtualisation extensions. All Modern AMD processors have this. Some Intel processors don't. You want this. If nothing else, if you get a processor without this you are cheaping out.
VT-D/IOMMU on the other hand is 'nice to have' IF you have a host that supports PCI passthrough and some other features. If you need to ask, you probably don't need it.
Ram is nice to have. The rule of thumb I follow is whatever my host normally uses (I assume 4 gb) + 2gb spare + whatever I need for my guests.
Number of cores might be a factor as well - depending on load and the number of guests. If you're going to be running a lot of VMs with heavy workloads you might want more cores - in my case I tend to run one or two, and even a dual-core machine does alright. A good rule of thumb might be one processor core per VM (though you can experiment with more, naturally). If the VMs are idle most of the time, naturally you can scale up.
Finally, VMs take up a lot of disk space, and obviously may be bottlenecked by throughput. I find a standard consumer grade HDD makes a good storage drive - tho some folk do need, and use much faster storage. Once again, depends on what your needs are. If speed's an issue, there's no reason you can't host your VMs on a SSD, or a SAN via a fast interface. You might also want to experiment with RAID, JBOD or simply having VMs on seperate disks and interfaces. I tend to use single VMs transiently, so my single large disk is sufficient