Representing the Lord on a mission field is a high calling. Since you're in a new place where no one knows you, your appearance can go along way toward opening doors and establish trust in the community. Dressing appropriately with conservative, professional items helps the public recognize you as a missionary.
Choosing the right shoes and socks is one of the most important decisions you'll make on your LDS mission clothes shopping trip. Shoes need to comfortable and durable as you'll be on your feet often. They also need to match your overall attire and message. That means you don't want to bring casual, trendy footwear that won't hold up or look professional.