You don't need professional equipment to get great results — but photo quality still matters. A good source image gives the system more to work with and generally produces cleaner, sharper outputs.
Use natural or soft lighting, keep the camera steady, and ensure your face is clear and in focus. Avoid heavy shadows and overexposure.
Keep your face centered with enough room around the head and shoulders. Avoid extreme angles that distort facial proportions.
Use the highest quality original image available. Avoid screenshots and over-compressed files whenever possible.