It depends on how fast a PC you want/need. I have an integrated graphics card, and it really isn't bad for Godot. It has almost no impact on blender, except if I have a really detailed mesh(~1 million tris). I've never noticed any lag with other specs, though some things in the engine might benefit from higher specs(e.g. load times). I have a pretty average PC, and I run Godot & blender just fine:
CPU: Intel Core i5-4210U CPU @ 1.70GHz(usually runs at 2.50GHz)
RAM: 8GB DDR3
HDD: 1TB HDD
GPU: Intel HD Graphics 4400(about as slow as graphics cards go)
These specs are perfectly acceptable, the main thing for me is the graphics card.
Keep in mind that you can replace parts on a desktop. If you see a good deal on a PC, you can get that and then replace just the graphics card if the graphics card isn't enough.