The Hellenists were those Jews who embraced Greek culture and were mostly from all over the Roman Empire. Some of the Hellenistic Jews (widows) complained that the others receiving better care so the solution was to find men who could do the job best, seven of them.
The apostles are far more concerned with the spiritual quality of the men than their outward appearance or image (of good reputation, full of the Holy Spirit and wisdom). The idea behind full of the Holy Spirit and wisdom is that these men should be both spiritually minded and practically minded. This can be a hard combination to find!