First up, the hew HL has the minimum spec declared as a GeForce GTX 1060 -- and the Oculus Rift will nag you in the menus if you're using less than a GTX 980, so you'll be wanting to upgrade your GPU too.
If you're not fully committed to VR, a second hand Oculus Rift or HTC Vive (the two "first generation" headsets) is the cheapest way in :)
The Oculus Quest can be used standalone or with a PC now ("Oculus Link") - if mobile VR interests you, then that model is ideal mixture.
WindowsMR headsets are ok, but less polished than the HTC/Oculus/Valve offerings. I'd consider them if you can find one at a good price and that's your goal (low price). The HTC/Oculus/Valve ones are pretty much equally good, IMHO.
If you want the full HL:Alyx experience, it's going to be optimized 100% for the Valve Index... which also has the fancy "knuckles" controllers.