The areas that you travel are on both high and low levels, so you need to be prepared for rain (we only had a days worth, but it was really heavy), with a good quality raincape (not £1 type) or long rain mac, as otherwise a short top has all the water running over your legs.
Good quality shoes for walking, I suggest the trainer type or all terrain shoes You do not need walking boots, it is for the rock paths. If you have problems, take a walking can to take the pressure off your leg when walking up/down stone steps.
When it was sunny it was extremely warm, a hat and sunscreen is required.
But it gets cold in the evening and you should take a fleece type top.
Early starts on safari means it is very cold at the start, but then can get extremely hot, so you need to dress in layers that you can remove during the day. Suggest basic t-shirt under a shirt and a cardie/fleece with light jacket.
I found it really funny when in Cape Town, I was in t-shire and light trousres and the locals were in fleece/jeans and wooly hats, as they felt the cold (20 degrees)
On the high levels, it is wind that can be cold, so again a layer system is suggested.
I envy those who are going as i want to go again, you will really enjoy it.
Just bring a book for the rather long coach trips that will be needed between bases.