building a new skylake system and want to know what psu would be best with some overclocking of the cpu and gpu
Any quality 650w will be more than enough. I'd recommend an EVGA G2. IF you want to SLI, get a 750w unit. No need for more than that.
750 watt would be fine. If its withing your buget I would get an 850 that way you can sli in the future.