Where Luqman is mentioned
Luqman is mentioned in Surah Luqman, which is the 31st surah of the Quran. His story is in verses 12 to 19.
It opens with the meaning that Allah had certainly given Luqman wisdom, and told him to be grateful to Allah. The verse adds that whoever is grateful is grateful for his own benefit, and whoever denies, Allah is free of need and worthy of praise (31:12).
So the first thing the Quran says about him is not his wealth or his rank. It is that he was given wisdom, and that wisdom begins with gratitude.