Pack lightly and plan to wash and wear, to leave plenty of room to fit in shopping. Metallicus stores have great, quick drying, no iron mix and match pieces that roll up to almost nothing, often on sale. Join the loyalty club at no cost and get $15 off a shop each month that you spend at least $1. Rinse clothes out each night in the basin, using soap/bath gel/shampoo provided, wringing out well, laying flat in a towel, rolling it up and twisting it. Hang clothes on clothes hangers in air conditioning and they will be dry by morning.
Add sunscreen, insect spray (Bushman’s), alcohol hand rub, camera, phone, iPad/tablet/power plug adapter, toiletries, underwear, makeup, hairdryer, ear plugs, first aid kit (consult your own medical practitioner for your individual specific needs, but ask about medications for treating gastroenteritis and cold and flu (and preventing malaria)) also documents including e-ticket, passport, visa, booking confirmation print outs, insurance details, money, ATM cards if using, small change purses.
A 70 Litre backpack with wheels and daypack/ small bag is ideal. (Kathmandu has some good options when they are on sale.)
It’s a good idea to pack essential items and a change of clothes in carry-on luggage in case checked-in baggage is delayed.
Also consider packing a light extra bag that packs thinly, to carry-on extra shopping or fragile items on the way home.