I got parts left below, should i complete it,
OR sell and spend more to build a Ryzen 2600 system ?
i7-3770 cpu
2x4gb DDR3-1600
450w PSU (crappy one from coolermaster but will be fine)
mATX Case
Only need motherboard and new one is $110. (ebay used mobo not cheap)
https://www.pcbyte.com.au/gigabyte-ga-b75m-s-motherboard
Usage: Light gaming (World of Tanks) + looking for cheap gtx1060-6gb before getting VR headset.
Your system is fine for light gaming (and definitely fine for WoT).
But VR… depends which VR headset you have, but upgrading the CPU could very well net you benefits. Whether those benefits are worth the $$$ is a decision for you, especially depending again on which headset and what games you're looking to play.