I have a judgement from Gwinnett County Magistrate Court against a resident of Gwinnett County who owns a rental home in Dekalb County. Is my judgement enough of a reason to file a lis pendens on the home in Dekalb?

Actually no. As I understand it a lis pendens is used while a court case is still pending. Since you have a judgement, its not appropriate. Since its commercial property you may be able to file a lien against it, but that doesn't get you anything until the house is sold. I would see if the tenant will let you see a copy of their cancelled rent check. Fromthat you can find a bank account to maybe attach.