For 2D? Not much. A 16 or even 10 series GPU should be more than enough, 20-series cards would be overkill unless you're gaming/rendering/etc. on the side. CPU and likely RAM may need to be pretty decent, though. As you'll likely be using a lot of Photoshop. To what end? I couldn't say, as I don't do a ton of Digital/2D art on a computer. Someone more experienced might be able to answer more concisely.
I'd get a decent PC and put the bulk of my budget into a graphic tablet (e.g. Wacom), though. Because you aren't drawing shit without one. Not on a PC, at least. It's one thing to manipulate a photo in Photoshop with a mouse, but it's a different beast trying to draw in Photoshop with a mouse. Assuming, that is, you aren't tracing. As for animations in 2D? I'm pretty sure most people doing 2D art/animations are using Live2D. But again, someone more experienced in 2D are going to be able to answer more concisely in that regard.
As for 3D? If you have to ask what the minimum spec is for that software, then it's probably just better to look elsewhere.