You can, its a bit cost prohibitive though.
Vive / index controllers need either a vive/index headset to sync to or you can use vive tracker / steamcontroller usb dongle where you need 1 per controller.
You then also need at least 1 lighthouse to actually track the controllers.
Steam vr should then be able to detect the oculus headset and then detect the vive / index controllers.
The piecemeal sales are more because the index controllers can be used with vive / vive pro systems that already have lighthouses and such.
That would be the worst, to come that close and have it not work. I lucked out and my roommate also picked up a system and his is going strong, so I'm just using it when he goes to bed..
I hope these issues aren't too widespread, don't want another red ring situation...
I'm about 5 hours in and for the most part I like it. My only complaint is damage feels inconsistent. I'm playing on hard so most things kill me in one or two hits I don't know how different normal is, but I'll have times when an attack that killed me from full health one time will do hardly any damage to me under the same circumstances another time. Between that and a few spots where checkpoints seemed a little far off led to a few frustrated attempts.