GIGABYTE Gaming Box RX 580 8G Graphic Card eGPU (GV-RX580IXEB-8GD) https://www.amazon.com/dp/B07CCK527Y/ref=cm_sw_r_cp_apa_i_b0beDb5CA0ARY
Edit: used through Amazon is $50 cheaper. I got my gigabyte 1070 egpu used through Amazon as well and it's been working fine
cool. yea the razer blade stealth has a thunder bolt 3. also u should look at other Egpu enclosures. I heard the gigabyte game box is pretty good for the price. comes with a gpu and has some extra usb 3.0 ports. for mouse and keyboard.Amazon Link
Let me explain from a cost perspective: it's not cost effective.
If you went with an egpu for your MacBook you'd need to grab something like a Radeon RX 580 with enclosure, at a minimum. It's about $400 on Amazon right now. This doesn't include the VR headset.
The problem you'd have is that VR needs, at a minimum, quad core CPUs to run smoothly. The Macbook would a very low power dual core CPU that doesn't provide enough power for VR tracking and gameplay. (You'll see jitters and lower framerates)
So basically going with the egpu would end up costing you about $50 more than the the Optiplex I mentioned and would perform slower, because it would be CPU limited.
The egpu method would only really work if you had a recent Retina iMac or a 15" MacBook Pro.
How about the gigabyte AORUS RX580? It is bigger than the puck, but smaller than pretty much any other eGPU. It is also more powerful, and costs less, coming in at under 400$ after rebate.
How much is cheap with regards to the card? You can get a brand new "mining" RX470 8GB that has a single DVI output for 130$ (assuming you are in the US). While the RX580 is about 20% more powerful, being able to connect the eGPU directly to the monitor provides a boost, so you should end up with better performance overall. If this is about the same price you'd pay for the RX580, it might be a better option.
A brand new, normal, RX580 is 190-200$ on Newegg right now as well.
The AORUS Gaming Box RX580 is 389.99$ after rebate on Amazon, including both card and enclosure.
Finally, if you do get the cheap mining card, you'll need an enclosure: The Power ColorGaming Station is 179.99$ as open box on Newegg. A brand new one is 199.99$. This is the cheapest fully-featured (87W charging, and a good PSU to support nearly any card, and even Ethernet and USB expansion) eGPU enclosure currently available.
If your laptop has thunderbolt 3 this would do nicely