if you want to go play a walk on where you are given no kit, you will need:
mask, marker, barrel sock, tank, hopper, pod pack & pods.
additional but pretty essential items are: playing gear (trousers, top), pads, footwear (suitable football boots).
after that there is an almost infinite number of items that make a day of paintballing easier including (but not limited to): squeegies, toolkits & spares, gloves, headgear, cloths (for lenses, inside hoppers etc).