Find a good and affordable laptop where you can use Kali linux and the associated tools.
Anyone is enough, because you can work well with 2GB of RAM, ram and a reasonable 4-core processor.
Doesn't have a desktop, but you don't need it if you know what Kali is for ;-)
Windows notebooks are best suited for this
I have the Trekstor Surfbook C11B-CO
Never, the good old DOS machines.