Gaspar Mission House is fully furnished so you do not need to bring any bath towels, sheets, pillows, etc. You will need to bring personal toiletries and any items that you would like to have as décor in your rooms.
As far as clothes are concerned you do need to prepare for four seasons. You do need to keep in mind you will have to walk to the bus stop and wait for the busses in rain, heat, humidity, cold, snow, and possibly ice (normally not all at the same time). Each placement differs on dress code and the director of Precious Blood Volunteers will talk about this after you are accepted.