A potential reviewer should be a qualified expert with thorough and in-depth understanding of the subject area of your manuscript. You can recommend researchers from other universities who are from the same field as you, fellow experts you meet at conferences and other academic forums, and authors you have cited in your manuscript as potential reviewers.
However, you should not recommend colleagues who work in the same department, employees who work under your supervision, your own supervisors, or co-authors, as this would involve a conflict of interest.
(Note: Editage does not recommend reviewers for your manuscript.)