I highly recommend you try proxmox to get the most potential out of you system. Basically can run many services and vm with little overhead, dynamically sharing the specs.

Now about those specs… what everybody else said really but heres some pointers:

You don’t need a big dedicated gpu unless your doing something that explicitly demands it. They are tricky to setup with virtual machines also.

If you plan on running a minecraft server i recommend at least 8gb ram. Anything else will probably run fine on 4. You can probably run quite a few things on 8gb but ram is cheap and its nice to have some extra room.

For cpu, the more things you do the More sense it makes to have more cores. If you plan on buying then amd ryzen x y z is you best option where.

X is the number you want higher Y is a number you should not care about as much Z is potentialy the letter “G” for graphics, they are often more expensive. Get them anyway because now you dont need a dedicated gpu (and even if you already own a gpu. Trust me you will thank me if that one ever has issues)