You don't really need much to practice Yoga. Loose fitting clothes to allow freedom of movement and flexibility are a must.
Jogging suits,shorts,and breathable materials are best.
Socks are also used in yoga for hygenic reasons. Be sure to use socks with grips to ensure your footing. Mats are used to provide a clean and hygenic space to sit, stretch an lie on. They are very light weight and easy to carry with you. There are also many types of props, DVDs, and music that you can purchase to provide help, instruction, and ambiance to your practice.