When sourcing dresses, the material is the primary determinant of price and durability. You should prioritize suppliers that provide detailed fabric specifications, such as GSM (Grams per Square Meter) for thickness and fiber blend ratios (e.g., 95% Cotton, 5% Spandex). For high-end garments, request OEKO-TEX Standard 100 certification to ensure the absence of harmful substances. Always ask for colorfastness test reports (Grade 4 or higher) to prevent bleeding during washing, especially for vibrant or dark-colored evening wear.