I just started Muay Thai a couple of months ago and for my first session I just had shorts and a tshirt, and a bottle of water. They should provide you with anything else you need for the mean time. Just ask your instructors, they should be happy to show you what to look for when buying equipment, and how things should fit. Even now I only use hand wraps, ankle supports, gloves, shorts, tshirt, shin pads and when sparring possibly a belly pad (which I doubt you will be expected to buy) and mouth guard. Enjoy, it is awesome!!