Clothing/Shoes/Weather Gear: The spa provides crisply ironed white cotton kurtas to wear during your stay. I quite liked the idea. It is pleasing to the eyes to see all people dressed in whites rather than find somebody dressed in florescent green or yellow. It integrates well with the natural green environment.
This really depends on the time of year, it does get very cold in winter but snow is rare. We were here at the end of the rainy season, hot and wet, so a folding umbrella would be useful. Sandals make for sensible footwear; it saves you ringing out your socks on a daily basis, as the rainwater can get quite deep. We didn't take much in the way of sun protection, as it tends to be cloudy for the most part. Most kinds of clothing, to suit your time of visit, are available in the town and much cheaper than in your hometown, wherever that may be.
Toiletries and Medical Supplies: No special medication though we'd all had a hepatitis A jab a while ago and kept our tetanus dosage topped up. The local doctor is brilliant at flushing out any impurities you may have picked up on your journey here; Rishikesh is very clean by Indian standards.